Motion sickness?

Do any moms here have little ones with motion sickness? My 2 year old has had multiple instances where he has thrown up in the car during long drives. As far as we know, he is not allergic to anything, but my husband thinks it’s due to milk because each time he has thrown up a milk product. For instance, twice he has thrown up milk because that’s what he had to drink prior to traveling, and another time he threw up cheese balls he had snacked on before traveling. He has thrown up another time and it was just water. He drinks milk fine every day and has never had any issues with dairy products. I’m certain it’s due to the motion of traveling and not milk. I plan on mentioning it to my sons doctor at his next appointment, but are there any precautions I can take to help him in the meantime?