During long road trips, back before iPhones and the like, my mom would have us pick out a book and buy it for us to read to keep us entertained while driving.

That worked fine for me, I've never gotten carsick, but for my sister could never do that; after reading for not much time, she would start feeling nauseous. Initially I think my parents thought she was exaggerating to get attention, but eventually she puked in the car because of it and they suddenly had no issue believing her.

It eventually led to them buying a cheap TV/VCR combo and a cheap power inverter for the cigarette lighter and using that for road trips, which didn't seem to bother her very much.