How do you sleep? On a satin/silk pillow case? A sleep cap (this would be really good for short hair)? These methods generally reduce frizz while sleeping because the friction between your head and your pillow is minimized.
If you already do one of those things, and find that your hair needs a little more help to be restored to its glory, try a refresher. Some people use water, some use watery conditioner, some even use some oil concoction. I'd judge it on how your hair feels when you wake up.
After smoothing down frizz with a refresher, let your hair dry and then fluff it a bit.