Springtime Stout is the May brew from the Brew of the Month Club.
All members of the Club get free sample of the brew in their in-game mail at start of May. Should you want more, your local Brew of the Month Club Brew Vendor sells it in stacks of six till the end of May.
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 "Flower Child: Springtime is here!" buff for 10 sec. Through these 10 seconds, several flowers will grow around you.