Yes, as Jerry says, it is important to make sure he is getting water. You could also boil some meat or fish in a little water, and let the water cool, and give that to him. It may interest him more than plain water. Or you could dissolve a little honey in water, so it is sweet. See if he will drink it normally. If not you will need a plastic syringe with NO NEEDLE attached. Then give him fluids into the corner of his mouth with the syringe.
He must get water or any fluids. This is very important, or he could get dehydrated, and that is dangerous.
Try him with plain cooked meat, chicken or fish, and some rice. Just plain food like that. See if he will take some plain boiled chicken or fish. Nothing else for now, until he shows signs of feeling normal again.
It may be that raw food right now isn't such a good idea just in case he has an irritation or infection in his gut. My feeling is it would be better if the food was cooked at the moment.
The next thing is to find out what is causing his lack of appetite. How far is it to drive to a vet's? Maybe he wouldn't feel car sick if you stop very often to let him out of the car for a short walk. This will take ages to get there of course, but if he is more comfortable that way it might be a wise thing to do.
Have you noticed any other symptoms? Does he pass worms or worm fragments when he defecates?
Hopefully this is just a tummy upset which will pass
Hard to recommend, but for sure your dog must drink water, try to get some water down if the dog isn't drinking water.
Do you have some food, especially meat, that you can share with him. Dogs in general love meat. You don't have to make a meal for him just something to get him started. When I say meat, I mean red meat, chicken and fish. Cooked better, but a little raw red meat may trigger his appetite
If you are tying to get him to eat dry kibble, you might try grinding (food processor or chopping very fine with a knife) that with raw carrots, or other vegetables: green beans, celery and so on. You may need to add a few spoons of water to help blend the mixture. No need to make a large portion, a small portion will establish his interest/willing to eat., .