it's better than rabbit turd ice, it's better than hospital ice, i haven't had sonic ice yet, but this is really good--
i just fill the ice trays 1/3 to 1/2 full with perrier, it's soft and white and chewy and many pieces are hollow in the center and it also breaks apart really easily.
so far i also tried pellegrino and another off brand of sparkling mineral water but the perrier is definitely better than the pellegrino, the pellegrino comes out harder and more brittle. i didn't try with just plain carbonated water, i think the minerals in the perrier help make it softer and chewier.
the best way to enjoy it is to pour room temperature mineral water over the ice to soften it up and the bubbling mineral water enhances the chewing...