A light brown ring has formed around the edge of the drain in my bathroom sink. I have tried applying bleach directly, but does not work. I do apply a "bleach foam" on that sink daily, so don't understand why that happens. Any suggestions to get rid of it. Thanks

I will make a suggestion after others have taken a crack at it.

What is the sink material? If it is a composite, synthetic marble or such, it will be very difficult.

Try CLR or LimeAway or http://www.the36thavenue.com/how-to-clean-a-porcelain-sink-2/