Especially if they are made of pvc.
How to get rid of mold in bathroom sink drain.
You do not want to use boiling water because it can damage your pipes and connections.
To remove black mold in the drain you can scrub it using a brush or a piece of cloth.
Rub all parts in the structure thoroughly including the grate that is possible to be infected by black mold as well.
Next get about 5 6 cups of very hot water not boiling and then pour it down the drain to wash away the dead mold baking soda and vinegar or hydrogen peroxide.
Removing mold in sink drain mold collects in the drain tailpiece which is the vertical pipe that extends down to the p trap and on the undersides of the strainer and stopper.
If you have difficulty in reaching small parts of the drain you can take it apart for a while and fix it back after the cleaning is done.
Rinse and repeat the above steps as necessary.