Verse 11. And have no fellowship. See the sentiment here expressed fully explained See Barnes "2 Co 6:14"

and following.

The unfruitful works. The deeds of darkness that produce no benefit to the body or the soul. The word unfruitful is here used in contrast with the "fruit of the Spirit," Eph 5:9.

But rather reprove them. By your life, your conversation, and all your influence. This is the business of Christians. Their lives should be a standing rebuke of a sinful world, and they should be ever ready to express their disapprobation of its wickedness in every form.

{a} "with the unfruitful works" 1 Co 5:9,11 {b} "reprove them" 1 Ti 5:20