“Alcohol is a mild poison” has been a house rule within my extended roleplaying circles for a long time. It fits well into almost any setting or metaphysics, and allows you to do interesting things with intoxication.
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Oh yes, although with roleplaying setting metaphysics, it's probably good to define this to be true if you're using it in your game. (To make sure it interacts with the rules correctly and has the right keywords etc etc.)
For example if you cast "detect poison" do you detect bottles of alcohol, or a hidden wine cellar, etc etc. If your DM has never considered whether or not alcohol is a poison it probably wouldn't occur to them to mention it, but if they have then they might!