Preheat your waffle iron and lightly coat it with cooking spray.
In a mixing bowl, combine the cooked white rice, rice vinegar, mirin, sugar, and salt. Mix well until the rice is evenly coated with the seasonings.
Scoop a portion of the rice mixture onto the preheated waffle iron, spreading it out evenly to cover the surface.
Close the waffle iron and cook for about 5-7 minutes, or until the waffle is golden brown and crispy. Repeat this step for the remaining rice mixture, making sure to spray the waffle iron between each batch to prevent sticking.