The one time I will highly encourage sports drinks over water, is during tournament situations. During tournaments, you sometimes play two or three games per day, and in that situation it's very important to replenish carbohydrates, which is what the sports drinks provide. It's critical in those situations that carbohydrates be replenished as quickly as possible, within the first two hours after a game. This allows the body to replenish the building blocks for energy more optimally. My father always had me suck on an ice cube encrusted with rock salt.
Ice cubes can be effective because they are ingesting fluid.
However, I would still highly recommend drinking water, in addition to the ice cubes to ensure they get an adequate amount of fluids in their body. As far as rock salt, it's probably not necessary for youth players to eat rock salt or take salt tablets. The American diet provides ample amounts of salt to ensure there's enough salt in the system for a match. However, it may not be a bad idea to simply add a little table salt to their meal the night before the game. Salt is basically an electrolyte, and electrolytes help maintain a normal functioning of several systems within the body, such as with muscular contractions, and temperature regulation.