Hi Gneiss -- This is an interesting thread you got started!
I've had many dreams about drinking and/or using. I have a ton of dreams in general, always many dreams each night (and have had lucid dreams), so this isn't really that weird to me. BUT I do know what you mean about them being disconcerting and scary etc.
I have a slightly more positive outlook on it; from what I understand, dreams can also serve as a learning vehicle where our minds can "practice" confronting the things it is trying to learn during the day. I can see how this could be interpreted as prelude to relapse, BUT also could be seen as your brain battling something that you may not be aware of day-to-day but is a fear or something your mind needs extra "practice" on. So, I see my drinking dreams, as unpleasant as they are (and I had one last night, so your post is timely) as a good thing overall, a chance for my brain to work out these bigger issues in a safe space.
Just a thought!