Here is a body weight workout you can try that I did today.
pushups 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10
atomic crunches 4 sets of 25
side planks 45 sec -1:30
pushups 10sets of 10
Do the a set of pushups then immediately do crunches then back to pushups once you have done the crunches sets go to planks for a couple sets then to side planks you should end at the 10 pushups.
Then go straight to pullups and knock them out with 45sec-1 min rest between each set. Last thing do 10sets of 10 pushups and then stretch. Its a great quick workout that will give you the stamina and strength needed to do many pushups especially for your Army PT test or what ever test you have for your self. Make sure to focus on your form in pushups and all the way up and down on your pullups. Don't cheat your self. Get strong!