Fine dust badge for foreigners

Hello together, does someone know how a foreigner should behave with his car in the environmental zones from summer on? Don’t drive in at all? Or ignore? Or what? In concrete terms, it’s about my grandpa who lives in Poland and has an older Benz and comes to visit me from time to time. He doesn’t get German badges at all in Poland… The problem should probably affect all tourists who want to visit German cities with their car / caravan… Thanks for Info`s