Re: How are these supposed to save energy
"Microwaved some coffee, put a spoonful of brown sugar in it, ,,, and WHOOSH"
It's essentially an example of kinetic v thermodynamic effect. Thermodynamically the water has enough ( more than ) energy to boil but no initiating pathway. In the lab we used little fragments of glass or wooden sticks ( added before reaching boiling I might add) to promote smooth boiling. Your sugar just trigger very rapid boiling. Almost like a mild explosion in fact. Cryogenic liquid gases added to room-temp water can sometimes behave in a similar manner - the initial turbulence promoting more and more rapid mixing until the evolution of gas become very violent.