Metok's Bubble Bock

Metok's Bubble Bock is the April brew from the Brew of the Month Club.

Source
This is only available to members of the Brew of the Month Club, which can only be joined during Brewfest.

All members of the Club get free sample of the brew in their in-game mail at start of April. Should you want more, your local Brew of the Month Club Brew Vendor sells it in stacks of six till the end of April.

On the first of April, members receive the following in game mail:

Effects
Like any weak alcohol, this makes you slightly drunk. Also, like all Brew of the Month brews, drinking one of these will create a Empty Brew Bottle that can be targeted and thrown.

Special effect of this brew is chance to get "Bloated: You feel bloated." buff for 5 min. While the buff is up, your character will breathe small bubbles, and removing the buff spawns a large "Brew Bubble".