There is a logical reason why I suspect artificial sweeteners are being put in many products now with as little fanfare as possible. Sucralose is made from sugar, but like other artificial sweeteners is far sweeter[1] than sugar, by around 3 orders of magnitude. I'm not sure about prices on an industrial scale, but moderately large quantities of sucralose without fillers seem to be about $50/lb, and sugar seems to be about $0.44/lb in 50 lb quantities. Thus, sucralose is around 110 times more expensive, but 300-1000 times more potent. The economic logic of treating sugar with chlorine and putting it in everything seems inescapable, as long as the public doesn't become sensitized.

[1]https://en.wikipedia.org/wiki/Sucralose

Edit: I don't know whether or not McDonald's in particular is using sucralose. I'm suggesting that it's a general trend, probably helped by the general public's distaste for things like aspartame, calories, HFCS, and so on.

the burger isn't especially unhealthy either. The burger patty itself is just beef. They don't add sugar or anything else to it. It's delivered frozen to the store so there are no preservatives. The buns are delivered a couple of times a week from the bakery so there are no preservatives in them either. A burger at McDonalds is really no worse than the burger you'd make at home, assuming you would buy typical grocery store ground beef and hamburger buns. The cheese is pretty much the same sliced American cheese you would get at the supermarket. The ketchup is from Heinz, or Hunts.

The deep fried stuff I would avoid. The french fries, fish, chicken, it's all cooked in vegetable oil. Years ago they used beef lard, until they were pressured into switching. Now we know that cooking in vegetable oil is pretty much worse in every way but they haven't changed back.