It depends if I'm going to have to remember the lyrics for the guitard. Last show we played I have 2 old fashions and decided to just stick with water after that(Just incase I got a curve ball)... not once...not twice... but three times I had to tell him the words to the songs... words he wrote... Thats what you get with a diva that doesn't want to practice before a show and "wing it" geeesh I was up 20 hours that day, worked third shift teh night before, went to school right after, THEN had band practice with our opener, band practice with our rhythm guitarist, and band practice again with rhythm guitarist and drummer... when we finish a few songs the guitard shows up and starts taking down equipment...he did not practice a single song before hand... I learned 3 new songs that day and taught the rhythm guitarist one of my originals... Sad because we didnt get to play it for the show...
But I digress back to your question.. I am Wisconsin native. We should know how to drink, that and I am a million times better player at a show then practice, not sure if its the energy or just anxiety or nervousness but when I'm on stage I make extra effort to try my best and not let anyone down. That's how I am personally though, so a few drinks may not bother me.
HOWEVER you do well to keep in mind that if you are drinking you should take it extra easy, not that a beer will put you over the edge but you have no idea how many people will be buying you shots that night, that is a factor beyond your control and I've seen even the most talented professional bands get too tipsy on account of a high spender trying to get the band wasted with them...
It's a hard line, sure you can just pass them up and tell them no thank-you, but in Wisconsin that's a good way of letting people think you're an *******. People want bands to be down to earth people that will drink with them, regardless of reasons turning down drinks will make you look like a snob...unless you are a recovering alcoholic then you'll get mad props and respect (at least in wisconsin)
So I guess in the end it depends on who you are and how much you can handle, I'd never say play drunk except at house parties where the audience ant tell how bad you suck. Or if you get in an extra band practice and you want to see how decent you can play wasted... never hurts to know the limits... lol
ALSO I will say if you are female try to keep drinking to a minimum, because girls look extra sexy when they are musically talented and guys will be buying them shots before they even play or know if they are good... Seriously I watched one of my fav female fronted bands get totally trashed just because one guy kept buying shots for her and the band(mainly for her) ..seriously like every other song, Eventually the guitarist stepped in and told the dude he needed to stop getting them shots or it would effect their playing... To which he got kinda pissy "COME ONNN BRAA ITS A ROCK N ROLL SHOW!" I can help but feel if she was just another guy she wouldnt be so subjected to peeps buying shots but eh it comes with the territory. Either way apparently she screwed up a bunch on keyboard (or so the bandmates told me)but it was a new song I never heard before and she still sounded amazing... lol guitarist was mad eyeing her the entire show as is trying to control her with his mind.... haha "dont you dare be drunk dont you dare be drunk!"