In the game I run we're pretty much drinkers* with a gaming problem.

Of five people involved, only one ever has to drive - one walks, two live here, and one rides with the driver (they're a couple, and each week decide which one drives). So yeah, good times.
* - and eaters - the alternate name for my game has become "Feasts and Foodies", much to my chagrin
In games I play in I'll almost always have a drink or two but nothing excessive as I have to drive home.
None of our crew smokes.
And, we now even have two game-specific drinks:
The Paladin - a hot drink made up of about 2/3 ordinary 'black' tea and about 1/3 rum; increasing the ratio of rum is optional. This gets its name due to the inventor disliking Paladins - this way he can kill several in a night.
The Necromancer - a stripped-down Caesar in a beer mug - a double shot of vodka, a good dash of tabasco, worcester sauce until it's brown, then fill the glass with chilled clamato juice. Stop there. Do not add anything else: no salad, no bean, no lemon, no other decorations - and fer gawd's sake no ice! This gets its name because the drink is about blood red in colour.
Drinking is allowed, so long as you’re generally still more playing the RPG than doing shots. Hell, we usually stock beer in the fridge and have a liquor cart that is a free-fire zone- everyone knows where we keep the hooch. And bringing your own is welcome, ESPECIALLY if you’re sharing. But do something stupid in game, and it doesn’t matter if you’re drunk: it stands. No drunk mulligans.*
We also expect players to be generally ready for their turn.
Absolutely agreed, particularly the no drunk mulligans bit.
* Hmmm...The Drunk Mulligans would be a fun band name.
To my considerable shock, a quick google search finds no band using this name - grab it now!
Lanefan