Optionally joining the Military here and I've done my medical tests so I can give you a list on certain criteria they look for and if you want to fail it.
Eyesight / Hearing
Physical Stamina (not being able to run long periods/fast)
Before most physical tests they do a blood pressure test, its known that lots of energy drinks like red bull can cause people to fail this
Blag a Medical disorder that will result in Medical Discharge, such as joint damage,shin splints or depression
Goodluck mate, personally dont think people should have to join up if they dont want to