Place a plunger over the sink drain and plunge it for about 10 seconds, just as you would plunge a toilet. You may need a small plunger if your sink is rounded and the plunger does not fit tightly enough over the drain to create suction.
Turn on the hot water and run about 2 quarts of water down the drain.
Pour 1/2 cup baking soda along with 1/2 cup white vinegar into the drain if the sink continues to drain slowly. Let the mixture sit for one hour.
Turn on the hot water and run about 2 quarts down the drain again to rinse away the loosened buildup.