My 5. year old. son. had. little. to no appetite. and. never. wants to. sleep. and. is always. thirsty. what. could. this be?

Normal 5 yr old: He does not have systemic issues with weight loss, fever, nausea/vomiting or change in elimination with urine or stool-sounds very independent and active and overall healthy. For foods/beverage offer and don't force. No emotional confrontations lead to more healthy eating at this age. Set firm limits about what is offered and when. He will decide how much to eat.