buy a tightly fitting T-shirt for your dog to wear during car rides

feed your dog several ginger snaps (yes, the people cookie) at least half an hour before taking your dog for a ride or try a few drops of ginger root extract, some droppers of ginger ale/ginger beer/ginger tea

don’t give your dog a full meal before taking him/her for a ride

place your crate in your vehicle so that the door of the crate faces the front, not the sides

dab a cotton ball into a shaken bottle of peppermint leaf extract (make sure that the label does not include the word "oil" and the volume of alcohol is less than 20%) then apply to all of the pads on your dog’s feet (This is good for thunderstorm anxiety, too.); give your dog some droppers of peppermint tea, or a drop or two of tincture of peppermint

try the homeopathic Bach flower essence called "Rescue Remedy"

begin a desensitization program (make getting into a stationary car rewarding; make sitting in a stationary car with the engine running rewarding; make traveling the length of the driveway rewarding, etc.)

offer your dog a little raw honey on some treats

Try Bonine an OTC medication specifically for motion sickness.  It
is chewable or can be hidden in a treat. It should be given at least 1/2 hour before leaving the house. The active ingredient is Meclazine (25mg dosage). 1 tablet is effective for a 20 pound dog