"Folkekøkkenet" (Community kitchen) in Ungdomshuset is a great place to come and eat a solid dinner very cheap and in alternative surroundings.
The food variates a lot since most of the food is donations and the treasures from dumpster diving. But the volonteer-kitchen crew always dish up with something interesting.
However a lot of people comes by, so to avoid long lines - be there a while before.
OR participate in the free hatha yoga classes in the house from 5-7pm, before hitting in the plates.