G'Day Jacob: While I don’t know what is growing in your beverage my guess would be that it is a mold (which can grow as white, fluffy masses) or yeast rather than bacteria. These soft drinks have a high concentration of sugar that many bacteria don’t like (although some strains of staph love it!), and at least for a while the beverage is/was probably acidic. Some yeast, molds or bacteria (e.g., acidophiles) would likely enjoy this environment but most would not.
I imagine once the beverage dries however all sorts of bugs could thrive in it.
see also - http://www.bcnlabs.com/beverages