For mere synonyms, you can always check https://www.merriam-webster.com/thesaurus/unimportant

Synonyms for unimportant

fiddling, foolish, frivolous, incidental, inconsequential, inconsiderable, insignificant, little, Mickey Mouse, minor, minute, negligible, nugatory, slight, small, small-fry, trifling, trivial

or https://www.thesaurus.com/browse/unimportant.

SYNONYMS FOR unimportant

frivolous, immaterial, inconsequential, insignificant, irrelevant, meaningless, negligible, null, trivial, unnecessary, useless, worthless, beside the point, casual, frothy, inconsiderable, indifferent, little, low-ranking, minor, minute, nonessential, nothing, nugatory, of no account, of no consequence, paltry, petty, picayune, second-rate, shoestring, slight, trifling, zero, zilch, zip

Although many of those words would imply that smoking is minute or negligible, (which is presumably not the intention), I would say that worthless, useless, and nonessential have the desired effect.