I was recommended to use
Bach's Rescue Remedy to ease the stress and anxieties of our little Geoffrey who was extremely nervous and timid when we first adopted him.
- ETA: I should have stated that some experienced hedgie owners recommend Bach's Rescue Remedy also for carsickness among hedgehogs - without this piece of info, my response might have appeared rather irrelevant to the OP's question; sorry for the oversight!

I put one drop in about 50ml of his drinking water every day. It's hard to say if the remedy had any effects on him. He eventually calmed down a lot, but it took almost 1-1/2 years. :lol:
Bach's Rescue Remedy was considered to be hedgie-safe at the time it was recommended to me. However, I later found out that the product contained alcohol - whopping 27%, in fact. So in effect, you're getting your hedgie drunk if you're not careful. My suggestion is to get
Bach's Rescue Remedy for Pets or for Kids as they're alcohol-free.
Some young hedgies get carsick easily and a few have green poo or even diarrhea, but they often grow out of it naturally. However, a few never do and continue to have trouble riding a car. You may want to start carrying your hedgie in a snuggle bag around the house and then gradually move onto to bringing him in a carrier on short car rides to allow him to get used the motions before taking him to a long ride. Keep in mind, however, that a few hedgies never get used to car rides and continue to show stress symptoms. If this is the case with your hedgie, you probably want to limit the number of car rides with him to the absolute minimum.