I actually created an account to share this with you. I do Tabata sprints on the tredmill when the weather sucks too bad to run outside in FL. Set the incline to 9 and the speed to 9 and proceed with the normal 20/10 interval.
If that's to steep or fast bring it down to 8 and 8, (10 and 10 to make it more painful or any combination you want). Do 8 rounds, 12, 52 or however many you can until you're too gassed to maintain the Tabata interval. These are easily just as taxing as sprints. Enjoy.