Answer: Christians are to have nothing to do with the fruitless deeds of darkness, but rather expose them, (verse 11).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
Having "nothing to do with the fruitless deeds of darkness" goes back up to verse 7 of Ephesians, chapter 5, where it is commanded (regarding the disobedient discussed in verse 6) of the child of God, "Therefore do not be partners with them." Children of God, who were, at one time, darkness itself, now live as children of light, learning and doing what pleases the Lord. We are even admonished to expose these fruitless deeds of darkness, because everything exposed to the light (God's Truth) becomes visible:
Romans 13:12-14: "The night is nearly over; the day is almost here. So let us put aside the deeds of darkness and put on the armor of light. Let us behave decently, as in the daytime, not in orgies and drunkenness, not in sexual immorality and debauchery, not in dissension and jealousy. Rather, clothe yourselves with the Lord Jesus Christ, and do not think about how to gratify the desires of the sinful nature [the flesh]."
2 Corinthians 6:14 through 2 Corinthians 7:1: "Do not be yoked together with unbelievers. For what do righteousness and wickedness have in common? Or what fellowship can light have with darkness? What harmony is there between Christ and Belial? What does a believer have in common with an unbeliever? What agreement is there between the temple of God and idols? For we are the temple of the living God. As God has said: ‘I will live with them and walk among them, and I will be their God, and they will be My people.'
"‘Therefore come out from them and be separate, says the Lord.
"‘Touch no unclean thing, and I will receive you.'
"‘I will be a Father to you, and you will be My sons and daughters, says the Lord Almighty.'
"Since we have these promises, dear friends, let us purify ourselves from everything that contaminates body and spirit, perfecting holiness out of reverence for God."
