I used to have a dog who would get sick in mountain driving.The vet gave him “doggy dramamine”. It worked the first time. The second time I forgot to give it to him and tried to drive slowly and carefully. He didn’t get sick and never got sick again.
The dog became acclimated to being in the car under different conditions. This is much better than giving the dog drugs. All of the dogs I know love to ride in cars, and they don’t care where you drive.
Why, may I ask, is this in the “repair and maintenance” forum?
Could this be why they hang their head out the window while driving ?