There are few meanings with the tobacco-flavored kiss to me.
- It sounds cool to the teenagers in Japan (and probly to other parts of world as well) beacuse hey that guy smokes! He is either a rule-breaker (underage smoker) or just becomes an adult. (LOL. Really, it sorta emphasizes on the time when people tend to be rebellious. Of course you dun need to smoke or get drunk to show that, but I believe most people tend to be more rebellious during teenage because it's the period they wanna prove themselves as adults, or that they can take control of their lives)
- the taste of bitterness from a kiss signifies the ending of the relationship. It also a taste she'll never forget (assume she couldn't smoke because she's a minor, and i dunno if she ever smokes... I just know she loves alcohols
).
- it beautifies the scene. It has to do with the wording. Like I said before, the power of Japanese/Chinese characters can be lost during translations.