You don't need much. Bring a kettle bell to a park near you, pick a few routines, repeat a few times, and in no time 20-30 min go by. It's fun. It's outdoors. It can help you get stronger and healthier.
Pay attention to form and posture when using Kettle Bells. Always engage your lower back, hamstrings and quads. Stay tight throughout all swings and exercises.