Billie Eilish rocked Spice Girls merch to hit the gym in LA (Picture: Backgrid)

Billie Eilish proved she is a Spice Girls superfan as she rocked a vintage band tee for a gym session in Los Angeles.

The Bad Guy singer, 20, reportedly spent three hours at the gym with a female friend, and was spotted leaving her session with a large water bottle and her boots under her arm.