Sugar is not far from being a drug in my opinion. It certainly feels addictive and has a definite impact on physical and mental state (especially true with respect to children). In that sense, it should undergo the same level of regulation...
https://www.webmd.com/parenting/features/busting-sugar-hyper...
I used to be boy scout. A week long camp typically gets lot more tolerable around day 3. At the same time the kids typically run out of candy and cell phone battery.
I'd say the problem is not high blood sugar from eating too much sugar. The problem is low blood sugar about 30min after eating all that sugar. And kids are great at keeping themselves busy enough, so they don't notice being hungry. But they do get cranky without exception.
And even then the problem is not the candy. It's the fact that they supplement "real food" with candy. And the blood sugar seesaw starts to reverb.
But here we are, needing to consume more energy because we do things (good, bad, useless or wasteful) with our time (and these things aren't directly looking for food.)