cherry yeast water

I've got a batch of cherry yeast water I've been brewing since 2 days ago. I recently put it in a bigger home, fed it a little snack of brown sugar (just a few sprinkles since I thinned it out when I transferred it,) and it's already developing bubbles. In fact, it's got enough bubbles developing on it that when I gave it a shake to mix it, the top popped off (since I've got the top on loosely to let out some CO2.)

Am I looking at bacterial activity, or is this just a really quickly-developing yeast? Or is this typical?