I didn't want to post a new answer but instead make a comment, but alas, not enough reputation.

I just wanted to add to Daemon Painter's answer and say that the final total bill also isn't working as it is multiplying a dict by an int.

What could work is to initialize out of the loop the total variable as well a new total_cost variable, and place:

total_cost += total

Inside the while loop but outside the if conditions. That way the last line can just be:

print("The total price of your basket is: ", total_cost)

Edit: the code, working as intended:

    price = {"Lemonade": 1.50, "Coke": 2.00, "Fanta": 1.00, "Water": 0.50}
    shopping_basket = {}

    print("Welcome to the online drink store!\nThese are the drinks we offer\n1. Lemonade: £1.50\n2. Coke: £2.00\n3. Fanta £1.00\n4. Water: £0.50")

    buy_another_flag = 1
    total_cost, total = 0, 0

    while buy_another_flag != 0:
        option = int(input("Which drink would you like to purchase?: "))

        if option == 1:
            qnty = int(input("Enter the quantity: "))
            total = qnty * 1.50
            print("The price is: " + str(total))
        elif option == 2:
            qnty = int(input("Enter the quantity: "))
            total = qnty * 2.00
            print("The price is: " + str(total))
        elif option == 3:
            qnty = int(input("Enter the quantity: "))
            total = qnty * 1.00
            print("The price is: " + str(total))
        elif option == 4:
            qnty = int(input("Enter the quantity: "))
            total = qnty * 0.50
            print("The price is: " + str(total))

        total_cost += total

        buy_another_flag = int(input("Would you like another item? enter Yes (1) or No (0):"))
    print("The total price of your basket is: ", total_cost)

In this case I would simply go for a while loop

while True:
    item = input("Please enter the items that you want to buy: ")
    if item == 'Stop':
        break
    elif item not in produce or item in slist:
        # error message or whatever
    else:
        num = int(input("Enter Quantity"))
        # other operations

Code Tells You How, Comments Tell You Why?

You have tried to document your code through comments, which is great! However, comments using # are mostly intended for other programmers, and is usually reserved for explaining terse parts of the code. A common way to document your code -- which is intended for the user -- is with PEP 257 -- Docstring Conventions.

As stated in the title comments (#) should be used sparsely. First you should first strive to make your code as simple as possible to understand without relying on comments as a crutch. Only at the point where the code cannot be made easier to understand should you begin to add comments. I would further break it down into three

1. Clarify the intent of your code through functions following the single responsibility principle
2. Clearify what each variable do through clear variable names that follows the standard python formating conventions
3. If the "why" is not clear through the first two points, then, and only then do we add comments.

PEP8 - Style Guide for Python Code

As to pick the lowest hanging fruits. Consistency is a key part of programming, as it greatly increases readability. It also tells a bit about the coders eye for detail. Lets' look at how you have named your global constants:

shopping_list = []

Pep8 recommends the following naming-conventions:

• CAPITALIZED_WITH_UNDERSCORES for constants
• UpperCamelCase for class names
• lowercase_separated_by_underscores for other names

Now to be fair you mostly follow this standard, which is excellent! I am just pointing it out that it is smart to follow these standards.

Handling user input

Jokes aside as a rule you should never except the user to use the correct input syntax. Instead you should build in checks, exceptions to handle these errors.

What happens if I write in help? A better way is to let a function handle the user input.

def get_valid_user_input():

    options = ["add", "done", "show"]
    print(MENU)
    while True: 
        choice = input("> ").lower()
        if choice not in options:
           print(f"Ooops, you need to enter one of the valid options {options}")
        else:
           return choice

Use of functions

A part that stuck out to me was

def show_help():
    print('What should we pick up at the store?')
    print("""
  Enter 'DONE' to stop adding items.
  Enter 'HELP' for additional info.
  Enter 'SHOW' to see your shopping list
  """)

A function should be a block of organized, reusable code that is used to perform a single, related action. Now, let us go through this checklist to see whether or not this should be a function

• Is the function called more than twice?

• Does the function serve a single purpose?

• Does the function perform an action?

  MENU = "What should we pick up at the store?\n\n
  Enter 'DONE' to stop adding items.\n
  Enter 'HELP' for additional info.\n
  Enter 'SHOW' to see your shopping list"
  

Since the answer to the last question was no, your function takes no input, so it could be a constant.

Note: As a general rule of thumb triple quotation marks should be reserved for docstrings and not be used for printing.

f-strings

f-strings are the new way of formating strings in Python, and you should usually use them. For instance

 print('{} was added to your shopping list!'.format(item))
 print('You have {} items on your list.'.format(len(shopping_list)))

becomes

 print(f"{item} was added to your shopping list!")
 print(f"You have {len(shopping_list)} items on your list.")

Nitpicking

• Put the parts of your code that are the ones calling for execution behind a if __name__ == "__main__": guard. This way you can import this python module from other places if you ever want to, and the guard prevents the main code from accidentally running on every import.

A deeper look

 What should we pick up at the store?

 Enter 'DONE' to stop adding items.
 Enter 'HELP' for additional info.
 Enter 'SHOW' to see your shopping list

 >

This would be better if it read

 Enter 'DONE' to stop adding items.
 Enter 'HELP' for additional info.
 Enter 'SHOW' to see your shopping list

 What should we pick up at the store?
 >

Secondly what happens if I am unsure and type in help? I am then prompted with the same menu.

 What should we pick up at the store?

 Enter 'DONE' to stop adding items.
 Enter 'HELP' for additional info.
 Enter 'SHOW' to see your shopping list

 > HELP
 What should we pick up at the store?

 Enter 'DONE' to stop adding items.
 Enter 'HELP' for additional info.
 Enter 'SHOW' to see your shopping list

 >

Not much help there I suppose. While this is semantics, you are handling user input both as an item, which is confusing. For instance

# If the user inputs 'DONE' exit the loop
if new_item == "DONE":
    break

A better solution would be to use a different name, such as user_input and later change it to item, when it should be added to a cart. I present a slightly different way of handling this below.

My own attempt

• I translated your comments into docstrings. They were well written and descriptive!
• I included the if __name__ == "__main__": guard.
• Bells and whistles I added typing hints, see PEP484.
• Your shopping list is better structured as a simple class. This makes it easier to maintain and add functionality. (What if you wanted to remove an item from your shopping list?)
• A more robust handling of user input. Try to write in something silly as input, what happens?
• I've separate business logic from user interface by doing my printing in main and keeping ShoppingCart clean.
• HELP was removed and instead a screen_clear() was added in addition to showing the menu every time.
• A numerical menu was added as an user enchantment. Whether you think this menu style is an improvement is up to you. If you decide to keep your style, at the very least do input("> ").upper() to allow users to do add. Numerical inputs are faster to input, can be clearer, and are easier to expand to more options.
• The menu and adding items were split into two functions (Remember, you used item for both).

code

import platform  # For getting the operating system name
import subprocess  # For executing a shell command


def clear_screen():
    """Clears the terminal screen."""

    # Clear command as function of OS
    command = "cls" if platform.system().lower() == "windows" else "clear"

    # Action
    return subprocess.call(command) == 0


MENU_OPTIONS = ["add item", "see your shopping list", "exit"]


def get_user_menu_choice() -> int:
    """Gives the user a menu to choose from"""
    low, high = 1, len(MENU_OPTIONS)
    error_msg = f"Woops, your input must be an integer in {low}...{high}\n"
    while True:
        print("Input a number from the list below:")
        for index, option in enumerate(MENU_OPTIONS):
            print(f" {1+index:>3d}: {option}")
        try:
            choice = int(input("\nPlease enter a number: "))
            if low <= choice <= high:
                return choice
        except ValueError:
            pass
        print(error_msg)


class ShoppingCart:
    def __init__(self):
        self.items = []

    def add(self, item: str):
        """Create a function that adds an item to the list"""
        if item != "":
            self.items.append(item)
        return item

    def get_items_from_user(self) -> None:
        clear_screen()
        print("\n\n\nWrite in the item you want to add to your shopping list!")
        print("[leave blank to return to menu]\n")

        item = self.add(input("> "))
        while item:

            clear_screen()
            print(f"{item} was added to your shopping list!")
            item_str = "items" if len(self.items) > 1 else "item"
            print(f"You have {len(self.items)} {item_str} in your list.")

            print("\nWrite in the item you want to add to your shopping list!")
            print("[leave blank to return to menu]\n")

            item = self.add(input("> "))

    def __str__(self) -> str:
        """Create a function to show all the items in the shopping list"""
        string = "My Shopping List:\n"
        for index, item in enumerate(self.items):
            string += f"\n{1+index:>3d}. {item}"
        return string + "\n"


def main() -> None:

    choice, add_item, display_items, exit_program = 0, 1, 2, 3

    cart = ShoppingCart()

    clear_screen()
    while choice != exit_program:
        choice = get_user_menu_choice()
        if choice == add_item:
            cart.get_items_from_user()
            clear_screen()
        elif choice == display_items:
            clear_screen()
            print(cart)


if __name__ == "__main__":
    main()

First of all well done, this is not bad for a first program :D

Good

• Usage of functions
• Using correct datatypes (dictionary for example)

Some Improvements in random order

• Read PEP8, the python style guide!

• fix your indentation

  it is standard to use 4 spaces indentation in python

• Prettify your code for better readability

  stock={'banana':6,
  'apple':0,
  'orange':32,
  'pear':15,}
  

  this maybe subjective but that is worse to read then this

  stock={
         'banana': 6,
         'apple': 0,
         'orange': 32,
         'pear': 15
        }
  

• uppercase can be simplified

  def uppercase(x):
      return x[0].upper()+x[1:]
  

  There is a builtin function for this

  >>> print("apple".capitalize())
  Apple
  

• Remove tripple quotes if they are not neccesary

  name=input('''What is your name?
  ''')
  

  There is no need to let this be over 2 lines, secondly maybe add a space for better UX

  name=input('What is your name? ')
  

• Use str.format() or f"strings" over old style formatting

  You use old style formatting alot "%s" % "somestring"

  it is better to use the new style formatting "{}".format("somestring")

  See String format best practises

• Use a if __name__ == "__main__" guard

  It will make your script importable while also being able to run from the CLI

  if __name__ == '__main__':
      name=input('What is your name? ')
      print('Hi, {}, welcome to my fruit store. Here is the menu:'.format(name))
      menu()
      ask_fruit(117)
  

• Avoid Magic numbers

  money=117
  

  Why 117? Because numbers can't have an explanation it is called a magic number

  Instead you can make it a global

  STARTING_MONEY = 117
  

• Instead of empty print() use \n

• Python doesn't really suit itself for recursion (recursion depth restrictions, memory consumption)

  def ask_fruit(money):
  fruit=input('''What fruit do you want?
  ''')
  print()
  if fruit in stock:
    if stock[fruit]>0:
      ask_amount(fruit,money)
    else:
      print('''Sorry, %ss are out of stock
      '''%(fruit))
      ask_fruit(money)
  else:
    print('''Sorry, we don\'t have that, look at the menu.
    ''')
    ask_fruit(money)
  

  Can be rewritten iterative

  def ask_fruit(money):
      while True:
          fruit=input('What fruit do you want? ')
          print()
          if fruit in stock:
              if stock[fruit] > 0:
                  ask_amount(fruit, money)
              else:
                  print('Sorry, {}s are out of stock'.format(fruit))
                  continue
          else:
              print("Sorry, we don't have that, look at the menu.")
              continue