I've had a puppy for a few months now...a failed foster. He spent the first few months of his life in a crate with no socialization. His first ever car ride was when some stranger grabbed him, wrestle...
This is probably more likely anxiety than motion sickness. Gradual acclimation can work, but I'd urge you to talk to your vet about anti-anxiety medication. It makes the leaning of calm and relax, don't be afraid, this will be a fun car ride SO-O-O-O much easier and faster.