The industry is already a step ahead on this stuff. I'm sure they have reams of market research that say "If a tax appears that causes Coke to be $1.49 per lit

The industry is already a step ahead on this stuff. I'm sure they have reams of market research that say "If a tax appears that causes Coke to be $1.49 per litre and Diet Coke is $1.29, there's a nontrivial amount of customers who will skip the soda rather than switching to the existing diet brand." So they need a product they CAN slide in if the shoe drops. They brought out "half-sugar" sodas about 20 years ago (Coke C2), but they hit the market with a thud. I suspect that the recent "Zero Sugar" brands are intended to fill the same spot. Notice how the branding is much closer to the sugared brand than the diet brands, and TBF, they're a lot more comparable taste-wise to the sugared versions than Tab or Diet Coke ever were. There's little case for introducing these products if it's primarily going to cannibalize their existing brands and consume already limited shelf space, unless there's some long-term appeal in it. But if there's a sugar tax, or some dramatic economic fallout that makes sugar ahistorically expensive, watch as the default position on the vending machine suddenly switches to suddenly Coke Zero.