-I will list bike to work even thoughit has been clubed to death in this thread.
-Don't take elevators, ever. Once a week I have to go to the 4th floor when I get to the university and I definitely feel that exercise everytime I take the stairs. Going to the 1st floor 4 time might not have as much impact but exercise = exercise.
-An non-perfected option that might show potential is to secure a squash sized bouncy ball to a elastic rope and secure that to the ground with a tent peg. Then start hiting it back and forth with squash racquets.
-Get yourself a hackysack/footbag (https://www.google.com/search?hl=en&q=hackysack) and find someone to play with. 3 meters from floor to ceiling is usually enough space. If you kick it higher than that then it isn't usually a well controlled kick. In my experience regardless of the effort you put into it, you be breaking a sweat after 10-15 minutes.
-Indjaca (https://www.google.com/search?hl=en&q=indiaca) is pretty much an outside only option that might not be as frustrating as hackysack to get into. Meaning you might get more people (even women) to play with. To break a sweat with Indjaca or related activities, I found that you have to hit it in a flat angle and put power behind your hints. More power means less accuracy which means you have to move more to keep it in the air.
The last three options can be played outside when temperatures reach ~10C.