As Christians, we are called to "go into all the world and preach the good news to all creation" (Mark 16:15). Clearly, bars are usually filled with people who need to hear the gospel. Further, many people will open up to a bartender more than they would to some other random individual, especially when they are intoxicated. So, yes, a Christian might have some ministry opportunities while working as a bartender. However, working and building relationships in a sinful environment, surrounded by ungodly music, the abuse of alcohol, and sexual temptations for several hours a day is clearly unwise. “What fellowship does righteousness have with lawlessness? And what partnership does light have with darkness?” (2 Corinthians 6:14).
Realistically, after a long shift of serving drinks in a bar, would the spirit of a Christian be edified? Would he/she leave with an increasing hunger for God’s Word? Would his/her mind be filled with holy images? Would his/her thoughts be that of Philippians 4:8? Scripture clearly teaches us to "hate everything that is evil and hold tight to everything that is good" (Romans 12:9). Perhaps a Christian feels he/she would enjoy interacting with unbelievers to share the message of Jesus Christ. But is that the biblical model of evangelism, to share in their lifestyle? Yes, Jesus ate and drank with sinners (Matthew 11:19); however, with a heart of true compassion, His primary goal was, and still is, to save sinners. He never indulged in their lifestyle; rather, He commanded them to come out of it and live godly lives (2 Corinthians 5:17).
Many refer to 1 Corinthians 5:10 when debating over whether we should work in an environment where sin is prevalent. However, Paul is not encouraging us to enter into full-time business relations with the “fornicators of this world, or with the covetous, or extortioners, or with idolaters.” He is simply saying we cannot escape their company altogether: “In that case you would have to leave this world.” But we must not spend huge amounts of time with those indulging in evil lifestyles—as is certainly the case when working in a bar—in hopes of having a moment or two in which to share the gospel. Realistically, not many bar owners would tolerate a bartender who spent a majority of his/her time evangelizing the customers. He knows that would be detrimental to his bottom line. The fact is that people who go to bars are not usually in any frame of mind to hear the gospel.
As Christians, we are to obey the commandment of God to “abstain from all appearance of evil” (1 Thessalonians 5:22). So “let everyone that names the name of Christ depart from iniquity” (2 Timothy 2:19).