Fill the bathroom sink with hot water, close the drain and let the water stand in the sink for at least 30 minutes. After 30 minutes or more elapses, check to see if the adhesive is softening and dissolving. Use the tip of your finger to rub the adhesive off.
Empty the sink and dry it if the adhesive did not come off with water.
Apply a small amount of either acetone or a citrus adhesive remover to an isolated spot on the sink to determine if it causes any damage to the finish. Allow the chemical to sit on the sink for a few minutes and wash it off. Look for any changes in the color or the texture of the sink. Wait several minutes and check again carefully. Fading may take some time.
Saturate a cotton ball or swab with the acetone or citrus remover and dab the adhesive spot until it is moist.
Wipe the adhesive with a dry cloth until it starts to come off the sink. Reapply the chemical solution to the adhesive as many times as necessary to completely loosen the adhesive.
Rinse out the sink to clean off any leftover chemical residue.