Edit: I can also see this with aquaintances who also believe in sugar highs: They only report this for the sugars perceived as worse than the "healthy" sugar sources, e.g. they project a sugar high if the kid gets a piece of cake, but not if it drinks 300ml of undiluted apple juice.
When it comes to a sugar rush, potatoes, rice, and corn have a significantly higher glycemic index than oranges, apples, and mangos (potatoes are about twice as high). This means that potatoes and corn will more quickly spike your toddler's blood sugar levels quicker and to higher levels. Does your toddler get more hyperactive after eating potatoes or rice or corn?
It may not have anything to do with blood sugar. The effects are usually too immediate for any sugar digestive action to have occured besides actual mastication.
Isn't bouncing off walls just a thing kids do?
to the downvoters: sugar rush is a myth. If you want to believe in food astrology you're free to do so, but you're WRONG.