This is a double-edged sword. On the one hand,
casinos give away free booze for good reason. Alcohol lowers your inhibitions, making it alot more likely that you will say, "Whattahey, all my chips on 4 black."
On the other hand, I'll never forget the time I saw, on
Poker After Dark, Gavin Smith, who was so drunk he spilled his drink and was slurring his words, come back from down 4-1 to beat Phil Ivey.
I play live cards in bars three times a week, and do not drink at all in two of them. But in my neighborhood bar, I get drunk, and I win there more. I won the championship for the last two month league there, and have been in the top ten every season for the last year.
I'm not readable, I don't get nervous, and I'm more agressive. My last two casino trips, I drank free Bloody Marys as fast as the waitresses would bring them, and made the final table both times.
But I'm a tight and patient player, and I'm still patient when I'm drinking. Especially in the casino, where I'm only getting free drinks as long as I last in the tournament. If you are already agressive, drinking might turn you into a maniac.
So my recommendation to drink when you play poker is somewhat guarded, and very conditional. What I do recommend though is smoking pot. As I always say, "Nobody can read you, if you keep forgetting what cards you have."