Try to get him used to it gradually.
Try sitting in the car with him for just five minutes on the drive, or wherever you keep it, don't even start the engine. Speak to him gently & make a fuss of him, then bring him back in the house & give him his treats.
After a few days, when this has become old hat to him, start the engine but don't go anywhere.
Next step is just a five minute drive, then a bit longer each time he's got used.
My two littlest ones were terribly sick but last week they travelled a round trip of 4 hundred miles without any sickness.
If it's any consolation, my twelve year old didn't like the car at first & was really sick too. By the time she was about 18 months old I had to drag her past every parked car or she was up on her hind legs trying to scratch the paintwork to get in
And it was a real picnic getting her past my car on the drive if I actually expected her to WALK somewhere instead of ride
