Schwarze Pumpe, located at the corner of Choriner and Fehrberlinerstrasse is a nice and small cafe who offers a good Brunch buffet on Sundays. The inside looks a bit like an old small factory with its pipes and industrial look.
The choice of food is kinda restricted, cheese, ham and stuff, sausages, eggs, fruits, salads, cereals, nutella, jams. But the price is very low (but not the quality of the products), one of the cheapest brunches I had, only 5 €, excluding drinks.
The atmosphere was very nice and so was the staff.