Our son was throwing food on the floor. Constantly. Compulsively, even. It was a game and we were losing badly. Our interaction went the same way each mealtime:
Son throws pea puree on floor.
“We don’t throw food on the floor.” Cheerful tone of voice.
Son continues throwing pea puree on floor, now staring us dead in the eyes and smiling.
“We don’t throw food on the floor, buddy. C’mon you know that.” Serious tone of voice.
Son now throws applesauce on the floor with a shriek of glee and another stare down.