My experience, for what it is worth...
The defensiveness that reared its ugly head, when I brought up the topic of alcoholism..was, for ME.. the one indicator that he REALLY WAS alcoholic. Even though he had claimed that he knew he needed to cut back/quit, if I said something, it turned it around. From something that supposedly was a normal "choice", if you can put it that way..it BECAME his battle cry of "I damn well wanna keep drinking and you can't take that from me".
When I realized I had to walk on eggshells, and could not express my own honest feelings, I think that is when I should have walked out.
I don't think I could go along (for myself) with fake beer. The message I'd be getting from that, is that someone really isn't secure enough in their choice to quit, that they can explicitly tell others that they NO LONGER want or intend to drink. Sounds more to me like they might be playing at the idea of recovery, but really are insecure at putting that message out to the "buddies" who are still drinking.
Just my thinking...