Motion sickness is caused by irregular and unfamiliar motion that disturbs the dog’s organs and sensory pathways of balance. Receptors located in a part of the inner ear called the “vestibular apparatus”normally help an animal process its body position, balance and movements.
A puppy gets motion sick because he feels anxious, or has fear of the "unusual".
Take small trips with him, stop every once in a while, give him treats, make the travel pleasant for him, and then slowly extend the length of the trips. Do not feed your puppy 1-2 hours prior of riding, and take him in the front of the car, with you, if possible.
That applies also for an older dog, with motion sickness. Same treatments.
Open the window a little for fresh air, and drive slowly around curves, and slow stopping.
On longer trips, let him come out for a while every hour or so.
If you have a dog suffering from chronic motion sickness, Dramamine and Benadryl are both anti-nausea medications for humans, but frequently used for canines.
Please consult your vet for proper dosing.