Sparklers, I don't see why not.
I use it all the time, even in Phase 1 and haven't seen any bad effects; unsweetened cocoa is allowed in P1, since it's in the ricotta cremes and, of course, milk and splenda are allowed.
I make mine with SF syrup and find that if I add the cocoa, SF syrup (same amount of syrup as the amount of sugar in the recipe on the side of the container), and salt in my cup, then mix it while the milk is heating in the micro, I can dissolve the cocoa pretty well in the syrup so that there are very few chunks in the milk. Yum! Using different flavors of syrup makes the cocoa interesting. My favorites right now are Kahlua and Toasted Marshmellow.
Enjoy!