One well known Scottish trio had (presumably still has), a "no drink before the gig policy."
If a group member drank before a show, that nights fee was split between the other two.
"You want to drink and play - no pay".

I don't know about it making me play better, but a few drinks sure make the audience look better.
Good thread. I agree, it's horses for courses, no drink on a concert platform, pint going flat during set, in a club, rowdy pub gig - a few beers of six.
love, john