Why $15.16? Because it's the law!

Well Kinda.

The $15.16 donation amount is a reference to the "purity order" , Reinheitsgebot , the German Beer Purity Law which dates back to the year of 1516. In 1516 the text of Reinheitsgebot stated that beer production must adhere to only using water, barley & hops as ingredients for making beer.