Baby wipes and a change of clothes. You'd be amazed what you can do with those in a pinch! As long as you start your commute reasonably clean, you're not going to get that stinky no matter how much you sweat on the way in.

If you have short hair, consider dunking your head under the faucet and rinsing your hair. If it's long, I find that letting the sweat dry and then brushing really thoroughly does the trick.