Baby birds eat whatever their mother gives them. Their mom will vomit her meal for her babies to eat they're not capable of digesting solid food. In emergencies, a baby bird has to be hand-fed by a syringe instead.Water or milk is not safe for baby birds to consume, and doing so can lead to happening by chance, drowning. The mixture you make for them mostly water, so they'll get all the filling with water they need.
Baby birds cannot handle the diet of an adult bird, so worms are out of the question also. Birdseed is also made specifically for feathered friends, infants should be fed only by their mother or by a syringe until they're around 15 days old. When they start showing interest in eating on their own by picking up things around the nest. When this happens, you can slowly introduce solid foods an adult bird would eat.