Without drill.....That would leave you sand blast and laser. Not too much office use sand blast now for cavity prep...It's messy.
The laser is a pretty good option. Not too sure what other guys talking about "more expensive". Laser is just another way to prep and you pay for composite. I have not yet met a dentist who charge more simply because they use laser.
Laser have some limitiation though, I personally like Biolase's WATERLASE. Awesome stuff for composite prep, simple soft/hard tissue surgery and someother procedure. ESPECIALLY for anxiety pt who afraid of shots...yes, you can actually get by WITHOUT shots (not all the time, though). Heard some even use it for crown prep, not sure how the margin gonna look like. Too bad it cost $50,000 a piece....been trying to convince my boss of getting one....
Oh, and electric handpiece is GREAT alternative, too. Still drill, but not as much sound, water, and vibration.