When I first started competing I would pack a bunch of water and Gatorade with me. I would take the powder and mix it.
However I found that Gatorade gave me sugar crashes after an hour or 2.
One tournament I only had water (and caffeine) and felt a nice smooth energy throughout the day.
I think most sports drinks just have too much sugar.
What works a bit better are electrolyte drinks. You can buy packets and mix it with water or just buy the bottles.
Electrolyte drinks help re-hydrate you a bit better than just water.
These days on competition day I drink 90-100% water and maybe 5-10% electrolyte drinks. My endurance feels good with that.
This is a cheap and really powerful electrolyte mix and it will last you a while:
Main Points
On tournament day, stick with caffeine, water, and electrolyte drinks.
Gatorade and other sugary drinks may lead to crashes later in the day. Don’t drink them.
Use electrolyte powder. It is specifically made to re-hydrate you as fast as possible. It will make you perform at your best throughout the competition day.