Raw fruit isn't a problem, not even for humans. Products where "sugar" is replaced by fructose or other, simpler sugar variants is. Various sugar substitutes are added to e.g. canned fruit in "juice" which is mostly some kind of sugar. Which lets marketing say "less sugar" ...

And "high fructose corn syrup" is ... almost pure fructose. Which the human liver can only process a limited amount per day.

Anecdote: a young guy in Freiburg (Germany) got Covid recently and as a result lost his sense of taste afterwards. Now he isn't interested in fast food any more as everything tasty "bland" and can "easily" eat vegetables which he disliked before, even broccoli or Brussels sprouts. Which made him loose more than 50 pounds. Don't get this wrong, it's not an incentive to get Covid, but an example of the effects of abstaining from fast food and soft drinks.