Kobe Bryant at the 2017 NACS show in Chicago.

Coca-Cola is buying a minority stake in a sports drink brand backed by basketball star Kobe Bryant, it said on Tuesday, seeking to mount a stronger challenge to top energy drink Gatorade.

The investment in BodyArmor comes as Coke's Powerade steadily cedes market share to its more popular PepsiCo-owned rival. Coke has also been rattled by falling demand for its fizzy colas.