In the downtowns middle of Saarbrücken you can find a very good store for only organic products including organic meat. Especially for your immidiate hunger you find inside a little cookshop. They serve many kinds of dishes like pizza, baked potatoes, pasta, vegetables and much more. All to take away or local consumption. Of course the opening hours are related to the store. So there is no chance to get there at night.
Cons: opening hours not at night