Mr. Biggs used to get car sick when we took long car rides (4 hr trips to miami). He would throw up a couple times if he had food/water before or during the trip. I spoke to the vet and he said not to feed him or give him water before we leave and to give it to him once we arrive. I did that and he was fine... just slept the whole way
Also, your vet can give you pills to calm your dog down so that he won't get anxious. I know they do it for dogs on the plane, but i'm sure they'd give it to you for car rides too.