Cats can sometimes get motion sickness. Sometimes this can be due to a disturbance in the balance organs of the inner ear. Motion sickness often manifests itself by the cat drooling or vomiting. Sometimes it even pees on itself or gets diarrhea.
Motion sickness can often be prevented by training the kitten to be in the car when it is stationary and that it gets positive experiences from the car. At the beginning of the training, it is good to run very short distances. After a short while, the car journey can be interrupted for a break. The length of the trips can then be increased slowly.
Some cats like to look when they go. The cage can, if possible, be placed a little higher in the car. Some cats may find it comfortable to lie in the dark. Then a blanket can be placed over the cage.
The risk of the cat vomiting is reduced if food is avoided a couple of hours before departure.
There are various aids against motion sickness such as soothing scent pheromones and supplements. Some are over-the-counter.
Ask your veterinarian or pharmacist for advice.
Avoid using your own medication.
For prescription sedatives, the cat usually needs to be examined by a veterinarian first.