Generally the whole of Germany has the Pfand system, where you pay a 25¢ deposit when you buy a bottle that you get back once you return it.
Tuebingen did their re-usable cups and bowl stuff to tackle trash from one time packaging like burgers, paper cups and so on. The city imposed a tax on the one time stuff that then “soft-forced” people to adopt the returnable packaging.
Honestly, it’s not much different to the refillable water bottles people carry around. Now people hand over their boxes to the Dönermann to get their Dönerbox.