Jucker in Uster lets you pick your own cherries and strawberries, and they have apple orchards as well so perhaps they would let you pick your own?
For Germany/Konstanz,
Mundraub is an awesome website which tracks "herrenlose" fruit-bearing trees (ownerless or stray, I guess) to encourage people to go pick and not let the fruit rot and go to waste.
Like Jucker, there's also "public" farms near Konstanz you could ask, such as
Gut Huegle.
Good luck, happy picking and please post back with what you find out!