Are you referring to the release of insulin in response to the intake of sugar? I believe the sugar high may just be a myth perpetuated by both the dopamine reward response, but also parents looking for explanations of children's hyperactivity. Kids are simply de facto hyperactive, there are disordered levels of hyperactivity, but simply: their motor cortex is overdeveloped and overactive relative to their prefrontal cortical control mechanisms (executive functions).
This difference in metabolism is due to physiology. It is not a myth. The implications of the difference are that energy created through the insulin process is immediately available and the unused remainder of energy after use is stored as fat. Fat in take, on the other hand, stores energy as fat the body thinks it will need and dumps the rest. Fat becomes energy when stored fat is metabolized in the liver resulting in slow but more consistent energy. Understanding that difference is significant to dropping weight.
I don't know about children, but its vaguely true about adults. Increased sugar intake alters the fat burning process with the gift of quick energy followed by a period of depression, a sugar low, that impacts body energy and mental concentration. The resulting behavior is slowed/faulty decision making and a desire for napping.
I suspect if this same metabolic change occurs in children it would slow a child's mental concentration thereby allowing less controlled behavior, which may present as hyper activity at the loss of self-reflection.