Rub all parts in the structure thoroughly including the grate that is possible to be infected by black mold as well.
How to get rid of mold in bathroom sink drain.
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.
Especially if they are made of pvc.
You do not want to use boiling water because it can damage your pipes and connections.
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.
White vinegar kills mildew and baking soda gently scours your pipes to wash the colony and any other accumulated grime out of your plumbing system.
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.
The best way to remove it is to physically scrub it with detergent and water so if you can remove the strainer and stopper to gain access to the tailpiece.