Many foods and beverages include ingredients whose sole purpose is to hide how sweet it is because otherwise it would be unbearable in your mouth. Gives you a stronger high once it reaches your stomach though.
Manufacturers design foods to taste good, not for some secondary effect of sugar in the stomach.
The idea that the sweetness would be "unbearable in your mouth" is just plain silly. People suck on lollipops which are pure sugar -- are those "unbearably" sweet? What you're saying doesn't hold up to even the slightest scrutiny.
Manufacturers aren't going to waste money on additional sugar and then try to undo the taste with other ingredients. That's not a thing.
It details many Concrete examples of exactly how the companies are manipulating everything about food for profit.
Kessler, further FDA head has written about this topic extensively as well.