Welcome to BYC. When they get so weak, it may be too late, but I would try to get it drinking water by dipping it’s beak into water for a second, and letting it swallow several times an hour. Poultry NutriDrench several drops is good, or SaveAChick electrolytes added to water. You can also use a tsp of sugar in a quart of water until you get electrolytes. Check it’s bottom to make sure the vent is not caked with dried poo.