If you do have to drill it, use a decent quality holesaw, like a Starrett. Note the holesaw and arbor come separately, and you need the correct arbor for the size of saw. Mark out very carefully, centre punch to give the drill a good start. Try and do the centre punch with the spot on the sink resting on some soft wood so the metal doesn't distort. When drilling start and push through firmly and continuously until the hole is complete. Don't slacken off and reapply pressure, there is a good chance the stainless steel will work harden. If you do have to pause, back the drill right off before stopping. If you can, support the hole area on a piece of soft wood, you'll get a better cut edge if you do.