Rooibos pronounced ROY-boss is a great choice for brewing kombucha for those with caffeine sensitivities since it is caffeine free! The flavor of kombucha brewed with rooibos is uniquely sweet and earthy. Even if you're not caffeine sensitive, this tea should be added to your kombucha brewing rotation to experiment and enjoy the delicious possibilities! Rooibos is an herbal tea grown in South Africa, whose name means "red bush.