OK. Well, orange stools make me suspicious of him having some sort of bile duct problem or hemolysis (destruction of red blood cells in the body).
Unfortunately the only way we will be able to figure this out is with testing (like bloodwork and ultrasound of the abdomen). Either of those two things can cause his other signs.
I really do not think it is from something he ate.
I also don't think this is something you can treat at home. Ideally you should get him to a vet. If you can't do that you can try the following to see if it will help but if he really has biliary disease or hemolysis likely it won't help.
1. Give him 20mg of Pepcid AC (famotidine). This is an antacid and may make him stomach feel better so he will want to eat.
2. Keep offering him water like you have been.
3. After the Pecid, wait at least one hour and then try to feed him. I would try offering him some bland foods like scrambled eggs, plain white rice, plain pasta. Do not put any oil, butter or spices on any of the food. Offer him small amounts to eat every few hours.
4. If he really doesn't seem any better in 36-48 hours you should try to get him to a vet.
Even if you can't afford a lot of diagnostics or treatment maybe they can give you some ideas on how to proceed. Maybe the vet will find something on physical exam that will point to the diagnosis without you having to do much testing.
I hope this helps. Let me know if you have more questions.