I was a Special Ed. teacher, always looked for answers to "why", but most answers not out there. Like my Ms - just happens. Dealt a bad hand - there are worse, there are better.
Mefozzie - not sure, but a psychologist told me his therory was Coffee (or as in your case Mt. Dew (both HIGH in caffeine) ) for Kids with ADD with hyperactivity and poor behavior control "gates", the caffeine helped raise their "gates". Much like a hyperactive student might take Ritalin or another stimulant to help him with behaviors. IMHO operant conditioning (rewards for correct behavior and awareness of what behavior needs extinguishing) in tandem with this works well.
A child (or anyone) needs to know what the boundaries are, what is behavior wanted, etc. Nobody should have to figure this out with cues, often not understood. Societal rules can be too subtle for some.
PPMS, DXed 2002 Queen of Maryland
Wise Elder no matter what my count is.