According to Simon Boswell, who worked with Red Bull in the early days, the brand had initially launched as a sports drink but struggled to gain traction due to a low rate of sale. However, the brand team identified an opportunity and adapted their strategy in order to leverage it (see Intended Vs Emergent Strategies). Apparently, a handful of stockists of Red Bull on the King’s Road in London were doing a roaring trade: on speaking to them, it turned out that people were buying it as a mixer to get a better kick from their vodka. Vodka Red Bull was born, and went on to become a phenomenon that transformed the business. To develop the opportunity, Red Bull focussed their sampling activity on students and used brand ambassadors to promote Red Bull as the essential party drink.
This video summarises why Red Bull's marketing has helped the brand be so successful.
Further insights and opinions about Red Bull can be found in this LinkedIn thread.