Resembling a shabbily comfortable living room, and usually packed, Weinerei Forum's main draw is the pay-what-you-want policy after 8pm, a divisive policy that'll either have you limbering up your liver in anticipation or throwing you into a very British whirl of indecision and muzzy-headed, guilt-induced social panic. In short the deal is you 'rent' a glass for €2 and help yourself to as much wine as you like, from an impressively-diverse list and basic buffet. At the end of the night, you contribute what you feel is a fair price.
Inevitably, the bar's policy has been a huge success - but you're expected to live up to your end of the deal with a decent contribution. Weinerei is staffed and owned by serious wine-lovers, so do expect dirty looks if you've been drinking all night and then contribute only a few euros. It can get rowdy in the evening; by day it's a laid-back café serving reasonably priced soups, snacks and coffee. Call ahead to reserve if possible.