Because of the climate in Germany, it is a perfect candidate for growing strawberries (at least in most parts of Germany). Look into the surrounding fields and see if any strawberry stands crop up in June-July. If so, you'll receive fresh and delicious strawberries that are cheaper than any you could buy at the commissary. As a bonus, some stands allow you to pick your own strawberries!
It is a great family experience to go to a field and pick your food. You can pick some as fresh and ripe as you want.
The photo above is a picture of the strawberries we got from our first trip and that entire basket of strawberries only cost 6 euro. You can see the size of the basket in the below photo. It was enough to split between two households and still have enough strawberries to last through a week of eating them every day.