It depends on how you categorize the fruit. For instance, apples are sweet but they don’t taste like sugar or sweetener. Some people would say there’s no sugar in them at all because they’re all natural sugars that come from the apple, but others might say that apples contain lots of sugar because of the high fructose content.
If you mean “which type of produce has the most carbohydrates?” then probably watermelon! If you mean “which crop has the most food energy useful for animals?” then probably corn! If you mean “which fruit has the highest sugar content per gram contained in it” then bananas are usually very high but berries are quite high too…