I tried Bissap juice (deep purple in the above photo) at the Bastille Day Fete in Manhattan on July 10. The woman who sold it said that Bissap was an African berry.
I discovered during an online search that Bissap juice is made from the dried red flowers of Hibiscus sabdariffa.
I thought it tasted a little like cranberry juice but with a perfume like essence. I was thirsty and it was a hot day. But if it was not served over ice, I probably would not have finished it.
Sources and more information about bissap: