So you do not have fancy equipment or enough time to strap on the running shoes and hit the streets. What do you do? Pop a squat. Or several. Squats can be easily made into a full body move that fits in anywhere.
For example, load up a backpack with a few heavy books. Put it on (not low-slung) and then do several anatomically correct squats. You will be sweating in no time. Squats also have different variations, allowing you to work every leg and gluteal muscle.