Way back when, my oldest was a bed-wetter, we kept extra clean sheets and towels in her room and she learned to get up and handle it when it occurred, then wash the sheets the next day. We initially tried rewards etc but ultimately we learned that her muscles just weren't developed enough and being a deep sleeper it was beyond her control. She stopped once the muscles developed (I think 10ish?). My youngest potty trained herself in a day at 18 months and never ever wet the bed. Kids just develop differently.