There is no particular way that you should sleep after a breast augmentation. If a 24-hour rapid recovery, no narcotic breast augmentation protocol is used, there are no restrictions on how you sleep, what you do, or the bra you wear (or not wear). You should be back to almost all of your normal activities and habits within 24 hours. You will, of course, not be healed, an over activity may be a little sore as might sleeping on your stomach, but you are in no way restricted.
Here is a video testimonial of one woman’s experience with the 24 hour recovery breast augmentation.