Reply #9: Two options I know of for sure:

[Jamastiene]

Pour baking soda in sink (down in the hole). Let it sit for about 10 minutes, then pour vinegar into it. It will sizzle and clean the sink to some degree.

The other option is to pour hydrogen peroxide into it and let it sit for about an hour in the trap.

In both cases, make sure you pour enough of the liquid part of the ingredients down to flush out the trap and rinse by running water after you are finished.

And yes, bleach is another alternative.