I find it hard to believe that a "sip" of beer would instantly enflame your acne. At worst it could've done that the next morning. If this (wheat) beer -> acne issue is consistent with you, check if you have a candida overgrowth in your mouth/gut, or if you have a gluten sensitivity. Beers in general have lots of carbs and carbs get turned into sugar by your digestive system.

You'll just have to test again. And if it happens again consider other possible relations to test: wheat, fermented foods, etc. There's something that forms in aged/fermented foods that some people are sensitive to. I can't recall it's name right now. But that would mean you want to eat the freshest possible foods.