Ostheim in der Rhoen is a quiet German town in northern Bavaria. Picture-book pretty, with narrow, winding streets, it doesn't seem like a place where anything — let alone anything hip — ever happens. But this bucolic hamlet is the birthplace of Bionade, an all-natural soft drink that's become a national sensation (it more than tripled sales last year), one that its creators now hope to export worldwide.
Bionade's founders don't dream of global conquest for its own sake. They speak passionately about what they describe as the drink's deeper meaning. "Bionade is a totally idealistic product. Of...