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, ...