One of the simple summer pleasures is leaving the city center to pick your own berries. The fields are relatively close to the city center as well and some are even accessible by jumping on the S-Bahn.
Depending on the time of summer one can find strawberries, blueberries, raspberries, and even currants. It's a fun family activity and the berries stay fresh much longer than those that are purchased at the store. Don't forget to bring an enormous bowl and some cash!