1 You can also use a toilet plunger on your bathroom sink. 2  Fill up the sink with water first, the use the plunger vigorously on the drain just as you would a toilet. 3  This will lift and agitate any blockage in the drain. It will smell a bit like vinegar for about a day. 2  You can also use a toilet plunger on your bathroom sink. 3  Fill up the sink with water first, the use the plunger vigorously on the drain just as you would a toilet.