depending on how bad the wrist is, you can do shadowboxing. If your wrist is really tender I wouldn't bother hitting anything for a week or two. You can focus on other things. Running or calisthenics. I sprained my back once really bad, I didn't hit a heavybag for a month but replaced the work with extra jumproping and calisthenics. Youd be foolish to keep working an injured body part.
well, you can do most cardio...swimming, running, eliptical, biking. You can life for legs. If you have a gym membership, you can hit the leg machines and you won't need your arms at all. You can also do most of your ab work as well. The only thing that should suffer is your upper body lifting and your striking/grappling. Just goes with the territory of getting injured. Watch some technique vid or read a technique book. You can at least shadowbox while you're waiting to heal.