And can traditional soda (healthy, probiotic) be exempt, and so then can be more competitive on price...

... I like this idea. I'd vote for that. :) ... depending on nuances of implementation. Perhaps it may prove more bureacratically complicated and expensive, and not worth doing. But all else equal, "simple and highly effective", sugar tax seems like a savvy equaliser, especially if was weighted for things like glycemic index, complete nutrient ratio to sugar, nutritional balance... oh, darn, this could get complicated fast.