You get so caught up in the game without even realizing you're just there for exercise
, and winning of course ;).
Since you said no equipment
, try jogging in in spot for 20-30 minutes. Your goal is to keep your heart rate beating fast to burn calories, so I'd say about every other minute run as fast as you can with proper form. In between the minutes, just jog.
I'm no expert, so try YouTube to see the proper running form, or how they do their exercise.