The Bible never refers to underage drinking specifically. In Bible times, wine was the beverage of choice, partially due to the lack of water in the deserts of Palestine. Everyone drank wine, and there was no cultural or biblical prohibition against it. The Bible only commands against drunkenness, not against drinking. There is no mention, therefore, of underage drinking in the Bible.
Scripture does not forbid a Christian from drinking beer, wine, or any other drink containing alcohol. In fact, drinking is often portrayed in positive terms in Scripture. “Drink your wine with a merry heart” (Ecclesiastes 9:7). Psalm 104:14–15 states that God gives wine “that makes glad the heart of men.” Amos 9:14 discusses drinking wine from your own vineyard as a sign of God’s blessing. However, the Bible specifically condemns drunkenness and its effects (Proverbs 23:29–35). Christians are also commanded to not allow anything to control them (1 Corinthians 6:12; 2 Peter 2:19). Scripture further forbids a Christian from doing anything that might offend other Christians or encourage them to sin against their conscience (1 Corinthians 8:9–13).
However, if the phrase “underage drinking” refers to breaking the law by supplying alcohol to minors or imbibing by minors, then clearly it is wrong and the Bible condemns it. Romans 13:1–7 makes it very clear that Christians are not to disobey the laws of the land but we are to obey the government God places over us. God created government to establish order, punish evil, and promote justice (Genesis 9:6; 1 Corinthians 14:33; Romans 12:8). We are to obey the government in everything—paying taxes, obeying rules and laws, and showing respect. If we do not, we are ultimately showing disrespect towards God, for He is the One who placed that government over us. Therefore, anyone who breaks the law by buying or supplying alcohol to minors is guilty of law-breaking and is disobeying God. Minors who drink alcohol illegally are similarly guilty.
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.