Last I checked, science couldn’t actually confirm nor deny the hyperactivity/sugar hypothesis. I’m going entirely on loads of anecdotal evidence here for that, considering the way processed sugars are already easier to metabolize, meaning they get to the bloodstream faster. High blood sugar = more energy, right? (I am not a scientist though, so it’s a good thing the sprites aren’t real, I get to play with the rules).
An alternative explanation, if it truly messes with your suspension of disbelief, the wood sprites are excitable anyway. They could just flit around because they’re happy about the tasty food.