Good question, and the answer is not entirely black and white. Personally, I’d be less strict if it was just a couple folks jamming for fun versus “we’ve started a band, this is practice.”
If it’s just jamming, set the expectation beforehand – stone cold sober, a couple drinks to loosen up, or “let’s drink and play until we fall down and see what happenzzzzzz…..”
If it’s band practice, my preference is no drinking, but one or two drinks consumed casually over the course of a few hours with no noticeable impact to the playing or the conversation is where I draw a HARD line. Practice is WORK, even if it’s fun, and you need to be on your game and focused or don’t waste my time and yours.
My $.02.