I do think he has picked up a gastrointestinal virus, parasite, or bacterial infection.
He may have eaten, or licked, something that has upset his stomach.
I would try giving him a human stomach acid reducer or pepto bismal.
1/4 of a 10 mg pepcid ac tablet, per 10 pounds of dog, every 8 hours
1 teaspoon of pepto bismal, per 10 pounds of dog, every 8 hours
You can try one or give both together.
Feed him small amounts of the plain cooked chicken and rice. No dog food for now.
If he seems to be vomiting mainly in the mornings, I would make sure you give him the Pepcid/pepto before bedtime. Also give him a little chicken and rice before bedtime.
If he is not improved by Thursday morning, he should see the vet.
If he can not keep food, or water, down for more than 24 hours he should see the vet right away.
I hope this helps.
If you have additional questions, please reply.