It seems that the situation of Sunday shopping is way stricter on Germany than in Switzerland, and unlike France.
I have been searching in Google maps for any non-culinary shop that is open on Sundays, and the closest to the ZH-Germany border is actually in Fribourg train station! No gas station, no rest stop, no other train station or family business. Nothing.
Is Google Maps missing something here? Do you guys know somewhere in Germany in decent distance to go shopping on a Sunday?
P.S. There are three gas station shops where I live. I am just asking out of curiosity.
Even in Switzerland, you will struggle to find anything but essentials on a Sunday, so I'm not sure what you are hoping to find? Any Sunday openings will be around Christmas but prepare for it to be a bit of a rugby match.