Are you reading or texting while riding in the car? If so, your eyes are perceiving different movement than your inner ear, which can bring on instant motion sickness in some people. Look around you, at the surroundings, so your eyes and inner ears are getting the same environmental data. The same principle applies to being in a boat, BTW.

What kind of car, and what is your riding position? Try changing positions. Being between the axles helps; being over the front axle, as with vans, can make things worse. Who is driving? Some people's driving habits promote motion sickness, and I am not kidding. My wife, on a bumpy road, will brake when she hits a bump, which means passengers are pitched upward at the bump, then foreward immediately after the bump. The ONLY time I have ever gotten motion sickness on land is when my wife was driving on a bumpy road. I keep having to remind her that there is no point in slowing down AFTER the bump.