Holy crap. How long is this test going to take from the first push-up to the last swim stroke? Sounds like a Frankensteined triathlon-ish plus bodyweight series, so I’m guessing it’s a couple of hours?
Like SBT said, for anything remotely endurance-related, Surge Workout Fuel is the first thing that comes to mind. It’s packed with electrolytes for rehydration (to avoid cramping and maintain performance), plus fast-acting carbs that won’t crash your blood sugar, and nutrients like beta-alanine and citrulline to further improve endurance and power output.
This talks a bunch more about why and how it was specifically put together: https://www.t-nation.com/supplements/the-legal-performance-enhancer
1-2 scoops sipped throughout the workouts, starting it about 15 minutes before training, would be the right approach. On game day, you could bump that up proportionally depending on how long the thing goes on, just be sure to increase the water intake the same, not just throw extra scoops into the same amount of water.
Like any sports event though, experiment with that higher intake beforehand because you never want to try a brand new approach of any kind (supplements, sleep schedule, nutrition, etc.) for the first time on the big day, even when that approach is well-planned.
I’d also include creatine because it’s time-tested to improve short-term recovery and increase strength and power. I’d like to think it’s almost a given that every lifter/athlete is using it, but just in case, yeah, it’s worth adding it.
And don’t worry about any “weight gain”. It’s not really water weight, like some people think. It’s intracellular fluid which basically helps the muscle do their jobs. Plus, the strength and endurance boost will far outweigh (no pun intended) 3-5 pounds on the scale. 5 grams per day, even tossed right into the Surge Workout Fuel, would be spot-on.
Finibars are the other great choice for fueling up during workouts and on the big day. It’s a special protein-carb bar that’s designed to be super-easy to digest, so having it between exercises/events won’t leave you feeling weighed down and sluggish and you can keep your energy up throughout the whole thing.
You might also want to post a thread over in the T Nation Combat forum. There’s a ton of current and former military guys who might be able give you some more specific input about the training, the test itself, or just to talk shop.