A video on social media showed world number one Djokovic falling to the floor after being hit by the object, which came from the stands.
The 24-time Grand Slam champion stayed on the ground for a while before being helped out of the arena in Rome by security.
“This is not being treated as a deliberate act, but as an accident,” said tournament organisers in statement reported by PA.
“A boy was calling out to get an autograph and the bottle fell out of his bag.
“Novak has undergone the necessary checks and has already left to return to his hotel. His condition is not a cause for concern.”
