Home Remedies for Pet Carsickness include:
Peppermint (Mentha piperita) and catnip (Nepeta cataria) are wonderful remedies to nausea and car sickness. Peppermint also regulates peristalsis, so it can help with irritable bowel syndrome, and even with symptoms of inflammatory bowel disease.
Catnip has similar effects on digestive upsets while being more palatable for felines. Even if your cat doesn’t experience a euphoric reaction to the herb — and 20 percent of cats don’t — it still has digestive benefits and can also serve as a mild appetite stimulant to both dogs and cats. It may help with some forms of vomiting in cats, but it’s important first to have your veterinarian determine the cause of the vomiting.
If your cat is attracted to catnip, you can just put some of the dried, crushed herb on the ground for the cat to roll around in. If not, you can add the dried herb to their food at the rate of around half a teaspoon per pound of food. You can also give cats or dogs a glycerin-based tincture (available at some health food stores), half a milliliter for every 20 pounds of body weight.
Glycerin-based peppermint tinctures are widely sold in health food stores for use by children. Dogs can be given these products dosed by body weight according to the guidelines on the label; those that also contain ginger are especially helpful for car sickness. (And yes, a gingersnap will also often do the trick.)
This article was taken from http://www.sfgate.com/pets/yourwholepet/article/10-holistic-pet-care-tips-you-can-trust-2483801.php#ixzz2H8GigNOH