Watermelon Brooke also advises to be cautious with watermelon, since it can have up to 17 grams of sugar per wedge (about one-sixth of the melon). But it's such a delicious Summer treat that you may not want to avoid it altogether; just be mindful of portion size. One cup of watermelon chunks is just nine grams of sugar. Image Source: Unsplash / rawpixel