re: Was it over when the Germans bombed Pearl Harbor??!!

Um, no, it is actually tea.

Tea is commonly used as a substitute for whiskey in film and stage. The problem with tea is it foams a little when jostled, and forms a small rim of foam around the outside of the top surface.

The tea foam is plainly visible in the bottle Belushi chugs. Look at your gif.

Also, unless he immediately puked it up, chugging a whole bottle like that would have put him in the hospital and shut down production for days. No way any director would let that happen.