@star 1. go to restaurant. "wegen gehäuftem diebstahl unseres mehrweggeschirrs müssen wir leider 50€ pfand einziehen. rückzahlung nur in bar möglich." 2. order a glass of tab water (not on their menu but they reluctantly hand it out for free) 3. drink half, say you'd like the rest as take away. pay 50€ pfand with card. 4. go outside, finish the water, immediately bring back takeaway container. 5. get ur 50€ back in cash.
basically, what this DB document is saying, is that if you request a reusable (in this case: ceramic) mug, cup, plate or bowl, glasses for wine, beer or softdrinks, or silverware to consume the food you buy onboard a DB train, you are free to take this cutlery/those dishes home, for free :3