Sprint intervals are great for burning fat. I found this routine a few years ago that could be an alternative to that.and also time friendly 15 minutes, but you do work up a sweat. It's 3 rounds of 5 exercises:
first one you do four squats and on the fourth you jump and do a 180 and continue that process for 45 sec. Then take a 15 sec break.
2nd You do rear lunges for 22 sec then switch legs 22 sec, the 15 sec break
3rd You do courtesy squats for 45 sec then 15 sec break
4th I seem to have forgotten the fourth exercise, figure you can sub something in there, maybe wall squats for 45 seconds.
5th Pulse squats you pulse four times and jump on the fourth.

This did get my heart going and legs were sore the next day so it was a good alternative to my leg day routine when I was short on time.