Grab a skipping rope and if there's a park bench around do box jumps on that for 30sec, do 30sec burpees, 30sec fast skipping and 30sec mountain climbers. Rest for 30 and repeat 5-7 times. I really like that routine. Using the same timing you could throw in some body weight squats, push ups (elevated if desired), tricep dips off some railing or the park bench or some crunches. Yeah sprinting on concrete can be hard on the joints too... Hope some of this helps, go HIIT! Oooh, also for fasted cardio, I like to go for a 10k run once a week 1st thing in the morn but to help with fat loss I mix a heaped tsp of instant coffee with a splash of water which also gives me a bit of a boost as I'm running on an empty tumtum.