Choose a stiff-bristled brush made from a scratch-resistant material, such as nylon, steel wool or boar’s hair. An old toothbrush will also work and help get in between the cracks and small areas.
Rinse the sink and drain with hot water and pour a small amount of quality, greasing-cutting dish soap around the base of the drain. Scrub both the sink and the drain thoroughly, then rinse with hot water.
Sprinkle a thick layer of dry baking soda in and around the drain and allow it to sit for a couple of minutes. Do not add water. Scrub the drain with a damp brush, allowing the baking soda to clump. Continue scrubbing until all the baking soda is used and dirty. Rinse the sink with hot water and repeat if necessary.
Wipe or spray the sink drain with undiluted white distilled vinegar if the drain is clean and shiny, and allow it to air-dry. If stains and spots remain visible on the drain, plug the sink drain, pour full-strength vinegar in the sink and allow it to sit for two to four hours. Scrub the remaining spots with a brush, then drain and rinse.
Pour baking soda down into the drain to kill bacteria and odors inside the drain and pipes. Add vinegar and allow the combination to bubble and foam before rinsing it with hot water. Rinse the drain again with cold water, spray or wipe the sink with undiluted vinegar and allow it to air-dry.