So the *glass* part was the important part of your post? Not the beer? And the glass part of your post actually meant "glass", you weren't just using the word casually?
Well yes, glass isn't allowed. Not even sure where they got that glass!
I do have to mention that my beer mug from the Hog's Head in Wizarding World really really REALLY looks like glass. Especially when you're not right near it. If it was a mug with a hog's head on it, by any chance, it was plastic. Of course, that means the guy poured a beer into it since I really doubt he could have park-hopped with his beer from IOA.