I agree with Teachnk, if you keep feeding him table scraps, why would he want to eat his normal dog food? They won't starve them selves, but if he hasn't eaten for an extended period of time, a vet visit should definitely be in order.
It could also be from the stress of the long raod trip. He may just not be feeling him self from all the driving. A lot of dogs actually suffer from motion sickness.
Are you mixing water in with his food? Or table scraps?
IF youare concerned about him not getting enough water then you can try adding water to his hard dog food. I wouldn't recommend doing it all the time, but just to get him back on track again.