Slang name referring to a 50/50 mix of coke(or similar cola beverage) and fanta(or similar orange beverage). Normally this type of mix is made in fast food restaurants with a self-serve beverage dispenser. Tastes better than it might sound.
Teiresias says re
black orange: also known as
muddy water, around this
locale
TallRoo says re black orange: This delicious drink is a muddy puddle.