I don't mean to sound rude, but I am a wild bird rehabilitator and we have to tell people constantly NEVER feed birds bread. It could potentially kill the bird (or any) because their digestive system cannot handle the way bread is made today (such as added chemicals). I know a coot is not considered waterfowl, but a common waterbird, this is what we recommend people to do with any waterfowl they find and cannot get to a rehabilitator.
A youngster usually imprints on the species it is being raised by. Imprinting is not reversible and an imprinted bird can not be returned to the wild. Keep birds quiet and away from people and pets. Some waterfowl,such as wood ducks, can die quickly from the stress of simply being around people.The best way to help young waterfowl is to place the bird in a box with small air holes at the top of the box to provide ventilation and a towel on the bottom to provide traction and small (peanut butter jar lid size) dishes with water, chopped lettuce and/or cracked corn (NO BREAD PLEASE!). This is a very temporary diet. Waterfowl, like all young birds, require a special diet to prevent development problems. Providing a small stuffed animal or untreated feather duster will give some comfort to the bird. If you are not able to bring the bird to a rehabilitator right away provide supplemental heat by placing half of the box on a heating pad, enabling the bird to move away from heat if it chooses. Remember, even though these birds are able to walk and swim soon after hatching, their mother would still be brooding them to keep them warm.
Good luck with the baby! It's adorable