Hez most probably suffering from gastroenteritis and you need to take him to a vet as soon as possible as he needs fluid therapy.

Well, from the above data, I am able to diagnose it as canine parvo viral entirities , I hope the faeces is watery and foul smelling and ur dog is too much dehydrated and looks very thin within few days from getting affected from the disease and not taking any water too, if it takes water, then immediately it vomits, daily for 3 to 5 days, it should be given if fluids and antibiotics through iv ... Thank u...