Trainer suggestions:
-crate your dog. Sometimes the safety of confinement helps if it’s anxiety related, but at the very least a plastic airline style crate with a towel (if they won’t ingest it) will contain the puke.
-Blow air on them. I like the little ryobi fans if there aren’t a/c vents in the rear of your vehicle
-ask your vet about Dramamine/Bonine dosages. You can give it an hour before the car ride. If it’s anxiety related, a sedative can help
-no meals before a trip, but a ginger cookie can help settle a tummy