As of 2014, most commercially-produced root beer brands, including A&W, Dad's and Mug, do not contain caffeine. Certain root beer brands, including Barq's and America's Choice, and specialty root beers do contain varying amounts of caffeine.
If a root beer product contains caffeine, the manufacturer is required to list it in the ingredients, according to the U.S. Food and Drug Administration. There are also alcoholic versions that contain from 5 to 20 percent alcohol by volume. Root beer was originally brewed with sassafras roots until the FDA banned its use in 1960. As of 2014, most commercially-produced root beer contains a blend of artificial flavors, spices and natural flavors that mimic the taste of sassafras root.