Bretttûne No11 from Grutte Pier Brouwerij is a complex sour ale at 8% ABV, brewed in Leeuwarden. This experimental beer from the Bretttûne series relies on wild yeast and bacteria to drive fermentation, creating a fruity and dynamic character shaped by unpredictable microbial activity. The result is layered and evolving, reflecting the brewer's embrace of spontaneous fermentation techniques.

Founded in 2014 and named after the Frisian freedom fighter Grutte Pier, the brewery has become Friesland's largest craft beer brand. This Bretttûne exemplifies their commitment to brewing beyond convention.