Chemical drain cleaners (like Drano/Max Gel). While they work, they are expensive, bad for the environment, and can actually corrode your pipes if used incorrectly. Stick to the mechanical methods above first.
Follow immediately with one cup of white vinegar and cover the drain.
When your sink starts draining slowly—or worse, stops entirely—panic usually sets in. I tested the four most common methods to unblock a sink to see which ones are worth your time and which are just old wives' tales.