Don’t need to feel like you just broke your legs for a workout to be successful. You can do Tabata style training on a treadmill for incline sprints, stationary bike(on- high resistance, off- easy resistance, body weight exercises. 20 seconds on - hard as you can , 10 seconds off/rest Repeat 8-10 times.

You can do this before and after a workout before you cool down.

A lot of gyms have space for people to do HIIT. You can grab all the equipment you need, time and do it yourself. There are many templates you can follow if you don’t know how to design a workout.