None. Don't drink alcohol!
How much of alcohol is good for chess to play good.
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I'm a lightweight -- I don't dring hard liquor. So I would instead use beer in a shot-glass chess game. Since it will get warm, I recommend an IPA versus a stout. To make the game fair, they should have approximately the same alcohol content, ideally near 7.5%. If that sounds too weak, enhance the effects by using a time control of G/10 or G/5. But not any faster since it's a sin to spill good beer.
I can't find the link anymore, but I recall reading an account, written by one of the players, of a shot-glass chess game between an amateur and a master.
Naturally the master dominated at first, but since he had to drink the pieces he captured, he quickly got soused and started to blunder. The white glasses contained scotch, and the black glasses had vodka. The master's impaired state allowed the amateur to catch up and then get ahead in material, after which both players were well plastered.
One of them had been notating the game, but the next day it was discovered that the scoresheet had degenerated to gibberish around the 20th move, and the "chess pieces" were strewn around the floor amid puddles of liquor. No one knows the game result since there were no other witnesses.