Berliners tend to get a jump on their after-work drinking; it's quite common to crack open a beer on the U-bahn train home. Also frequently seen, a little later in the evening: teenagers drinking and vomiting to the swaying of the trains. American and British tourists, meanwhile, go bar-hopping with bottles of taquila in hand, eager to take advantage of relatively lax attitudes toward street drinking. And Berliners' traditional beer-soaked barbeques in public parks are, of course, sacred.
Although there are efforts to enforce existing bans on street drinking in Germany (particularly on public transport), and there have have been for quite a while, the practice is an important part of German culture, particularly in Berlin.
I spent a few months living in the Friedrichshain district of East Berlin last year, where my Polish neighbors excelled in public tippling far beyond even Berliner standards. They were installed drunk and inert on our front stoop, beers in hand, from 9am on daily, weekdays or weekends. Polish friends have assured me that drinking in front of one's building is a Polish classic, and therefore probably not a tradition that these men acquired in Berlin.