Less is more when it comes to training gear for Novak Djokovic ... 'cause dude went for a run on the beach in Spain wearing sneakers and a Speedo.
Djok was hangin' out in Marbella when he decided to get in a workout while taking in some sun -- so, he hit one of the public beach gym places and started grindin'!
... in his budgy smuggler.
He ran. He did pull-ups. Leg press. All while leaving little to the imagination.
Look, he's from Europe (Serbia) and was in Europe (Spain) .