As it seeks to respond to today’s sugar-wary consumers, Coca-Cola has been boosting the sugar-free varieties in its trademark Coke portfolio. And while critics might point to the potential confusion between brands (how many people know the difference between Diet Coke, Coca-Cola Zero, Coca-Cola Zero Sugar and Coca-Cola No Sugar?) CEO James Quincey says its two key sugar-free brands can co-exist happily together.