The fire at Tim Hortons, near Crystal Peaks, broke out during a storm on Tuesday, May 11, leading to speculation that it had been hit by lightning.
But an investigation into the cause of the blaze established that it was started deliberately.
South Yorkshire Fire and Rescue said the smell of petrol was detected at the doorway.
Unconfirmed reports online suggested a petrol bomb had been thrown into the restaurant.
A police investigation has now been launched.
South Yorkshire Police said: “Police and South Yorkshire Fire and Rescue attended the scene and the fire was extinguished and the building made safe.
“It is believed that the fire was started deliberately. The premises were closed at the time and no one was injured.
“An investigation has been launched and enquiries are ongoing to locate those responsible.”
The restaurant will offer seating for 118 customers.