Judging by my own experience, not my dogs', dramamine works but I and some friends experience a great deal of grogginess for a long time; I don't get that with Bonine, which works just as well. I agree with the "let him see" suggestion; supposedly what causes motion sickness is that your eyes are registering motion in relation to nearby objects. Looking at distant objects decreases the sensation of motion. Besides, if he can see out, maybe he can also get fresh air from a window? The only folk remedy I ever heard of is soda crackers, as a preventive.

None of this is guaranteed.

CC