For a small friendly game, its fine, but alcohol can impair your judgement. Poker is not a game to play with poor judgement.
But that said, when playing live, I always have a drink or two. Partly to loosen up because of stress, and partly to get vodka and redbull into me to give me the "I just hit a monster" shakes.
A "smoke" can be nice if it is legal in your jurisdiction. Relaxing without losing focus.
But if I was in a WCOOP event or something, no, stay away from booze. It will not improve your game...unless the problem in your game was excessive good judgement.
Cheers,
ObbleeXY