As a general rule, I don't drink on stage. I may have a rum & coke during set up, but from then on it's water or soda.

My partner likes his beer and swears he only has one during each break and brings one on stage. We're in our 50s and he just can't handle it any more, but does it anyway. I think this is one of the reasons we are playing less and less, employers see what I see, and that's a guy who isn't 100% all night. He's never drunk, just not sharp for that last set.