I feel your pain Dexter is the same way and he vomits too
it is stressful to take him anywhere anymore so i just leave him at home now as it stresses me out and i feel bad the whole time. He was not like this as a puppy. I got cerenia from vet but hate to give him a med to take him in a car.
I dread having to take him to vet as he had pancreatitis and when he starts vomitting he does not stop and so i hate to even chance the car rides for that reason as well
so sad as he is so social and i want to take him to meet ups as he would have so much fun but just cannot put him through the car ride