Cut all carbs and do moderate to intense cardio..........................
This.
Basically a 7-10 days before and on the date go on the keto diet and/or intermittent fasting, consume 3-4 litres of water a day, keep net carbs minus the fibre from the carbs obviously as that isn't as digestible to under 50-75g a day even less if you can handle it, do steady state easy cardio for 45-80 mins a day to deplete your glycogen stores which will help shed your body's water weight and easily burn fat for fuel. On this diet make sure you replace the carbs in calories with more healthy fats and protein. 10 days isn't much and you'll most likely drop between 6-10lbs in water weight doing this. Once you finish the test for the military you can go back to eating normal.
Note: The keto diet isn't really sustainable for longer than a few months as it makes it harder to meet your macros. it's just a tool so don't go overboard with it and end up busting your ass because it's just water weight not all actually fat loss.
Good luck, breh. I myself am trying to get into the Air Force.
One thing I've been told is that people train months on end to get fit but neglect practicing the aptitude tests so dedicate an hour a day to that as well as practicing 30 minutes to the interview questions they'll ask you because it REALLY matters. They turn away nutters and people who forget to practice the test frequently