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I'm lazy to explain the plot, so I'll just copy and paste it from the Beerfest Wikipedia entry:
"The plot begins with two American brothers, Jan (Paul Soter) and Todd (Erik Stolhanske) Wolfhouse, who are mourning the death of their immigrant grandfather Johann Von Wolfhausen (an uncredited Donald Sutherland), founder of the Schitzengiggle German beer hall in the United States. They learn from their great-grandmother (Cloris Leachman) that they have an opportunity to travel to Germany to deliver their grandfather's ashes. Jan and Todd gladly take this opportunity when they learn that Oktoberfest will be occurring at this very same time in Munich, Bavaria.
While in Germany, Jan and Todd find "Beerfest", an underground drinking game tournament run by Baron Wolfgang Von Wolfhausen (Jürgen Prochnow). As the brothers arrive, they witness the German national team defeating the Irish national team and discover that the German Von Wolfhausen competitors are relatives of the American Wolfhouse family. The Germans explain that Jan and Todd's grandfather Johann had stolen a beer recipe decades ago and demand the recipe back from the unknowing brothers. Jan and Todd engage in a drinking contest with the Germans but are soundly defeated. The brothers travel back home and swear to get revenge on the Germans...
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The humour in Beerfest is entirely over-the-top and ridiculously stupid, and it barely tried to be otherwise. When I was watching it with Justin (and Vivienne, a friend of ours from China), we were the only ones who laughed most of the time... the rest of the audiences were deathly silent. Scary.
There's not much I can say about this film, you either like it for its mindblowingly stupidity (a major character gets killed off, and is 'resurrected' in an unbelievable Deus Ex Machina, you don't see something like this happening in most films), or it leaves you disgusted. Highbrow fare this ain't, neither does this aspire to be a major work of art. But it's funny like hell. Best to watch with friends though.
Beerfest trailer