You're just unlucky. The taste issue is determined by genetics [1], although the grossest taste is often the result of sweeteners combined with aspartame, like Ace K.

Sweetener mixes are made so that most people will not taste a gross aftertaste. Some people will experience a bitter aspartame taste, and others will experience a very chemical aftertaste for other sweeteners, but the majority of the market doesn't.

[1]: https://academic.oup.com/chemse/article/38/5/379/360864

It's just how much you are used to it/individual preferences. Same thing as with any other taste, e.g. spicy food.

To me, sugar drinks feel displeasing. Aspartame doesn't taste like sugar, but it's sweet and that's fine. Most of the taste is the sour one from CO2, citric acid and phosphoric acid anyway.

Same here. It's not even the difference in sweetness, it's just the disgusting aftertaste that lingers forever. I've never gotten how people can drink Coke Zero voluntarily. Too bad they only sell caffeine-free Coke Zero and not the caffeine-free regular where I live, so I gave it another chance not long ago, but noped out after the first sip. It's undrinkable.

Though I prefer actual sugar, some low-sugar drinks use stevia, which doesn't have the same drinking-chemical-runoff taste of aspartame.

The aspartame is the ass-part-ta-me.

Yeah this is really starting to cause problems as things like this sugar tax push companies into adding sweetener to their "normal" versions. I now can't simply buy a Coke and know it will taste like Coke - I need to inspect the packaging and check if it will taste disgusting or not.

It's fine that they exist but presenting them as being full sugar when they aren't is false advertising.

I've never seen a soft drink sweetened with Xylitol. Is this a store brand thing? Most soft drinks I encounter seem to be sweetened by a combination of aspartame and acesulfame K.

Xylitol seems to be common in candy (especially chewing gum) and deserts, but I don't think that's relevant to a soda tax.

Perhaps you know of a commercial soft drink sweetened with xylitol that I don't?