They drink beer.

The largest beer festival in the world is Oktoberfest in Germany. Several other smaller beer festivals are held all over Germany all over the year. The 2nd largest beer festival in Germany and probably in Europe, is the Cannstatter Volksfest in Stuttgart. Its popularity increases and more and more people come from around the world to visit the festival every year. Many other places have beer festivals styled as "Oktoberfests", but taken on its own the name is generally taken to mean for the Munich event. The second largest genuine Bavarian festival is the Gäubodenvolksfest in Straubing. The festival is similar like Oktoberfest but it has an own history and it is not a copy of the Oktoberfest, as is the Barthelmarkt by Manching, which even dates back to Roman times. The third largest beer festival in Bavaria is the Bergkirchweih in Erlangen, with the largest open-air beer garden in Europe. Not called "Oktoberfest", but very similar in character, is the Cannstatter Wasen in Stuttgart which starts one week later and is the second largest fair in the world. Smaller beer festivals similar to the Oktoberfest are common in Germany and take place throughout the year in most bigger German cities. Some of them go on later into the night than the Oktoberfest. Other beer festivals include the Hanover Schützenfest, the Freimarkt in Bremen, and the Hamburger Dom. Like the Oktoberfest and the Cannstatter Wasen, most German beer festivals are also funfairs. They are called "Volksfest" (festival for the people).

It's like going out. You usually go with a group of friends. There are tents with a lot of benches inside ("Bierzelt") where you can sit together at a table and drink beer, eat food, listen to music and talk to each other (if the music isn't too loud). The bigger ones (like the Oktoberfest and Cannstädter Wasen that Jura mentioned) also have a sort of amusement park nearby during the time of the festival. So there are several joy rides, or little huts where you can do various things (buy lottery tickets for that big stuffed plush animal you can give to your girlfriend, shoot different prices with air guns, and so on). Some people (especially some tourists) just go there to get really drunk. Basically all German towns, even little ones, have some traditional time in the year for a "Volksfest" following the same principles. The smaller ones are often nicer than the bigger ones Jura talked about. But if you really like the joy rides, they are better at the bigger ones, of course.