Cap, it turns out, has the same "problem" as Wolverine in that he is physiologically incapable of getting intoxicated. Unlike Wolverine, who can't get drunk because of his extraordinary healing abilities, Cap can't because of the super-soldier serum implanted into him. Because of the serum, he has an extraordinarily rapid metabolism, which means that whatever alcohol he drinks is quickly burnt off by his system. It's a shame you can't get hammered after a long day of fending off aliens and villains hellbent on taking over the earth.