This problem is noticeable here in Amsterdam too -- homeless people tend to just take the whole garbage bag out of the can, and empty it on the sidewalk so that it's easy to spot and collect all statiegeld (deposit) cans and bottles.

It looks like the best solution the municipality has managed to come up with so far is to attach metal cupholder-like thingies to new trash cans, and people are expected to put statiegeld bottles and cans there, so that others can take them later and get a refund. Though I don't know how a regular uninformed person is supposed to figure out what these cupholders are for -- it's not intuitive at all.