I worked as a vet tech for 9 years, and food is not important. The main thing is getting fluids into him. The sub-Q fluids should have held him over well for a while, now you need to give him plain, unflavored pedialyte. If you need to use something like a syringe, then do so. Just every hour give him some pedialyte, even through the night. If it were my dog I would take him to the vet, first thing in the morning. Do not force the food issue, if he does eat before his body is ready, it will set him back. I would also look around and see if he got into some poisen, since he is acting so lethargic. I will send prayers your way. Keep us updated.