Sure you can! There's a couple ways to go about it.
Bodyshops have a sticky gum like bit that works... it stays sticky forever... put three gobs of it down, one at either end and one in the middle. Won't hold things on at speed, but as the sill never sees any serious wind, it'll work fine.
Or go the anchor style - use drywall style plastic anchors, just make sure you use big enough ones that they bind nicely to the car body. It would suck to get them in there and not be able to remove the screws later.
Or, of course, you could buy new door sills from the dealer.