Take Your Vitamins
Third, some of the damaged tissues can come from something called oxygen radicals, a byproduct of metabolism, built up during exercise. Selected vitamins--C and E in particular--can help minimize free-radical buildup. So, getting some C and E during and after exercise is appropriate.
Load Up on Carbs
Fourth, the energy for games like soccer comes mostly from stored carbohydrates. When a player finishes a game, the carbohydrate fuel in the muscles (glycogen) can be very near empty, meaning the player is fatigued. However, if some carbs are taken in during exercise, the depletion of glycogen can be delayed. This effectively postpones fatigue, and a little protein helps get more sugar into the muscle.
Pushing fatigue later and later has two advantages. First, your team is running and the opponent is tiring right when most goals are scored. Second, a large portion of injuries happen late in the game so delaying fatigue can be considered a way to prevent injuries.
Ingestion of some carbs after training and games gets the refueling process started sooner and faster than if the process is delayed even by two hours.
"You mean I have to supply water, protein, vitamins, carbs during and after exercise?"
Only if you want your players to have a leg up on the opponents while also getting a head start at recovery for the next game or practice.
But that doesn't mean that you have to shop multiple aisles of the grocery store. There are a variety of sports drinks on the market that can be found in grocery stores, nutrition stores or sports specialty shops (especially cycling stores).
Just check those labels. Look for electrolytes, carbohydrates, vitamins, and some protein. The current research suggests that a 4:1 ratio of carbs to protein is the best. You can cover a lot of bases with a single product and be at a competitive advantage on your opponents who aren't as foresighted as are you.