Here is a very simple routine that I learned from one of my brown belts, John Mangual. All you need is a pull up bar and a stop watch. If you do not have a pull up bar, find a wall or a fence you can climb.
Rounds are 1 minute in duration. You have to complete the following exercises:
A) 5 pull ups
B) 10 push ups
C) 15 squats
If you finish before time, you can rest. Once the minute is up, you repeat the exercises. Your goal should be to so as many rounds as possible. If you are unable to complete a round, you are done.
A good goal is to shoot for 15 rounds. That is 150 pushups, 75 pull ups and 225 squats in only 15 minutes. Give it try tomorrow and let me know how it goes!