Any chance of making it so when you slap a (non-magically) sleeping person, there's a chance they wake up?

I found myself wanting to do this recently as part of an rp interaction, and 'so and so wakes you' just didn't have the effect I was looking for. 'You sit bolt upright as a flash of pain runs across your cheek. So and so slapped you!' would have been much more satisfying.