If you can find a copy the d20 EQ system has rules on drunkenness, an alcohol tolerance skill, and magical alcohols.

Basics, from memory, is you make a skill check when you drink. If you drink enough to get drunk you giant a bonus to Str/Con and penalty to mental stats. If you fail your skill check the mental penalties are higher.

Various drinks also provide metabolic bonuses to stats, magical abilities, or make you smell funny.

I personally think every game is improved with things like Skunk Breath Ale, Bootbeer, and Armadillo Ale.