I think you've missed sight of the point of those taxes, which is to reduce consumption of actual excess sugar, not to tax things that taste sweet.

Both are unhealthy its not clear that fake sweeteners are better for you. Why tax a different kind of unhealthy less?

I'm no fan of artificial sweeteners or sweet things in general but the scientific evidence is pretty overwhelming that most of them are far healthier than sugar.

Because the scientific evidence overwhelmingly shows that artificial sweeteners _are_ better for you. They have no proven health impact and eliminate calories. The idea that they're somehow "just as bad" (or even worse) only comes from sugar and corn industry lobbying and marketing efforts.

Non-sugar sweeteners are better for you in at least one significant way: they have almost zero calories.

...but that’s the idea. They want people to drink the artificially sweetened version instead. That’s what the tax is for. If they taxed both the same it wouldn’t work.