I like to keep hydration simple and its important to use the same stuff for training, competition, and longer endurance events like our challenges. I also want stuff I can pickup at just about any convenience store. And remember that eating healthy is for wimps.
I like pure water in a Camelbak or any other sort of bladder system. I can refill them with bottled water from a convenience store or filtered water from just about any faucet. There are cleaning tabs that can be used every other day or so and only take a few minutes.
I like Gatorade in 20 or 32 oz bottles for the electrolytes and sugar. Yes sugar. There is nothing wrong with sugar when you are paddling, running, walking, working, exercising --- and sweating. I can buy Gatorade just about anywhere and it has worked for decades.
You can also get Gatorade in powder form so it is easy to carry all you need and mix it as needed. The bottles are reusable. But most of the time I just carry a lot of bottles at the start of the challenge and the load is consumed daily. It's just simpler.
On hot days with lots of paddling or pedaling I will consume 2 parts Gatorade to 1 part water. If there is good wind and I'm not working as hard it would go the other way around.
Always carry at least two Ensure Completes (or whatever brand you prefer) per day and have one before zonking at night. Do this even if you also eat something else.
Regarding actual food, it's easy to get the protein, carbs, and fat. Just make sure you get the fiber you need as well.
But we are all different. So find what works for you during the derby. Then stick with that during the challenge.
I almost forgot. It's important to have a recovery drink after intense workouts. The best one out there is a Fosters Ale in the big green can.