Situated in the ultra-trendy MQ opposite the entrace to the Museum of Modern Art, Halle has everything from a six-euro lunch to gourmet food - and it all tastes great. For the times when you're hungry and prefer quantity with your quality, you can go for the Cheeseburger or the Club Sandwich. Both are excellent, and both will keep you full for the rest of the day. Even if you speak no German, you may want to ask for the German menu, as the lunch specials are not printed on the English one.
Right opposite Halle near the QDK (Quarter for Digital Culture) in MQ is Kantine. Not as big as Halle, and with less "upmarket" food while still being of high quality, you can get a great filled pita or Asian here, as well as soups and breakfast.
I don't even think it has a name, but here it is, marked on the photo. And on the map. Best döner and dürüm I've ever eaten in, well, anywhere. Lean, tender, grilled chicken meat with tomato and yoghurt sauce, all packaged with onion and salad. If you've ever only eaten Swedish kebabs - this is nothing like them. The kebabs served in northern latitudes are rubbery strips of brown meat. These are not. About as addictive as crack cocaine these greasy divine gifts from Turkey make for an excellent snack or late night emergency food.
This ice-cream bar just north of St. Stephen's is probably the easiest and most pleasurable way of gaining weight. My preferred mode of doing so is the strawberry crepe, seen to the left.