After you work out, wash your sports bra in the bathroom sink and drape it over a towel to dry. The next day, you'll see it hanging there all fresh and clean, and you'll be motivated to put it on and work out again!
You'll save water and money by hand-washing in the sink, rather than running a whole load of laundry with just a few items. Added bonus: it cleans your bathroom sink at the same time. Now that's a time-saver!