A baby squirrel is supposed to be fed on scalded milk with a small 1 c.c. syringe very slowly 4 times a day, every 5 hours. You can also give it water with an eye dropper or let it lick water off your finger.
1 Additional Answer
Baby squirrels can have the same diet adult squirrels. Their diets consists of vegetables, fruits, dried foods, nuts and seeds. When faced with hunger, they also eat insects, meats, eggs and small birds.