Listen to this ^^^^^.
Get out of the sun as fast as possible after the games. This is more geared toward long endurance events- But I'd say that a 90 minute soccer game falls in that category-
https://www.slowtwitch.com/Training/Solar_Radiation_on_Performance_5870.html
Definitely have a cooler full of ice on the sidelines for everyone to grab and place on their bodies. You can pre-pack it in ziplock bags or just have bags nearby for players to jam some ice into when they need it. (You won't want to eat/drink this ice). Your player might want to have their own supply of ice to eat/drink. One bottle of water per player is not enough for warmup/gametime/halftime/post game. I think you need at least 60 ounces of water for game day. Maybe even a backup in case someone knocks yours over and spills it.
And make sure your coach is smart about it. Players with headaches, players who say they are "cold" or have a fever need to be subbed out immediately and probably be done for the rest of that game (if not the entire weekend).
How do you know if you are dehydrated? If your urine is darker than usual- you haven't drank enough water. The darker (and more it smells), the worse off you are.