At that age it's fairly common. I have found that getting them to lay down can help. Seems standi g on those spindly teenage legs can make those curves worse.
Try an open window and a closed window - one dog will be better with a closed window, another will be better with an open window.
Some dogs do better in the back seat, some in the front seat. Some do better being able to see out the window, some with no window view.
Just try different ways, keep it positive, and don't let him get dehrydrated.
Most dogs grow out of it after a while. I had a foster dog who threw up within 10 minutes of getting in the car. I adopted her out ans 6 months later she was living fulltimein an RV and had her bed in the backseat of the pickup. She never threw up again and traveled all over the continent.