I met them in the supermarket. They are all made of a plastic box similar to that in a quick-frozen jiaozi, cooled and then put into a disposable lunch box. Besides, they also send things like vinegar in ultra-thin plastic bags. As for what documents, I really don't know. Business license and hygiene license are necessary. But you can ask the supermarket what they need, and just prepare what you need. Let them sell it.