Upon drinking the Bubble Bock, now and then you will get a buff called Bloated. After five minutes (or after you click the buff off) your character will burp righteously, and a named Brew Bubble will spawn and wander around aimlessly for awhile before popping. You can target it, but you can't cast things such as Baby Spice on it, unfortunately. The bubble can also merge with other bubbles, so get some friends together and try to make a great big one!
It's actually somewhat interesting that they chose to name this brew a Bock. A brew they describe as light and bubbly would actually be pretty dark, unless I've confused my beers somewhere. Bocks were often used and praised for their nutrient content, because compared to light brews, it could actually keep you fairly sated during fasts and period where high quality food was scarce. A bock was not the best choice for this particular brew! Again, though, I could be totally wrong. I don't even like most beer.