Possible Clues:

• Brand at www.rootbeer.com
• Classic root beer brand ... or a hint to the answers to this puzzle's starred clues
• Competitor of Mug
• Root beer brand, and a phonetic hint to the three vowels of 18-, 23-, 37-, 55- and 60-Across
• Fast-food chain known for its root beer
• Brand now part of the Dr Pepper Snapple Group
• Barq's competitor
• Soft drink brand
• ''Initial'' root beer brand
• Classic root beer brand