If your dog doesn't eat for 24 hours it is not a big deal. It may just have an upset stomach. However if it is also not drinking then get to the vet. Also get to the vet if it has been over 24 hours. If it has been less than the 24 hours try boiling a boneless, skinless chicken breast and some rice or potatoes and feed that. It is a bland diet and shouldn't upset it's stomach.
If he isn't eating normal dog food then try something dogs like, like treats, or peanut butter, thats what my dog likes. It may not be healthy, but if he at least eats that, then put a little treat in his dog bowl with his food, make sure he sees that the treat is in the bowl. If you need more help, comment