If your dog suffers from motion sickness, drools or throws up in the car, there are things you can do to ease his suffering.
It is a great idea to sit with him in a stationary car and just get him used to the environment. Maybe bring a filled Kong with you, that he can munch on in the car, whilst you read the morning paper. Repeat daily until he is relaxed going into the car.
When you've done this often enough for him to be relaxed and happy to jump into the car with the engine off, you go through the same process all over again, but this time with the engine on. The car is still stationary though. Repeat daily until he is happy jumping into the car.
Once your dog is happy going in the car with the engine running, it is time for short, fun trips. First of all, you should make really short journeys to the dogs favourite places and not to (in their eyes) bad places like the vets, groomers, kennels, etc. You want to make sure the car journey ends with a positive association that will eventually spill over on the car journey itself.
Ideally you want to drive to a place so nearby that you can walk your dog home and collect your car without him.
There are natural remedies that you can give your dog before a drive, to help her cope with the stress of the journey. For example ginger and B6 vitamins. Even if the sickness is based on fear, it is still stress related and she could be helped by B6 vitamins.
There is also a specific herb called Scullcap & Valerian by Dorwest Herbs, which will help against travel sickness. The local vet sell them and I'm sure other vet practices and pet shops sell them too.