Toddlers are just werebears. The crash might be real, but there has been research into the "rush" part and its been shown that kids really don't get a rush. It's probably just confirmation bias on the part of adults. https://www.yalescientific.org/2010/09/mythbusters-does-suga...

Not saying we should feed our kids endless sugar, however.

I saw this with other parents when my son was small. So. Much. Confirmation. Bias.

I absolutely can feel effects from large changed in sugar intake, but the tiny things parents thought were evidence of a sugar rush were ridiculous.

Its not clear to me that the study disproves that kids do not get a rush from sugar:

"Dr. Tamborlane, also from Yale, reported that children given sugar had higher levels of adrenaline."

I'm not an expert in human biology but doesn't adrenaline increase activity?

Under discussion here is the long-term (not short-term) effects. The short-term effects are not, as far as I can tell, especially acutely dangerous, though they could be bad per se if experienced all the time (e.g. sleep disruption).

But toddlers can also be pretty wild with or without sugar. They sometimes get very excited when hungry, when tired, when woken from a nap, when lacking exercise, when frustrated, when separated from specific adults, when in conflict with other children, ...