What does Stanley do with his canteen after mr.sir fills it up?

After Mr. Sir fills Stanley's canteen, Stanley intentionally dumps the water out onto the ground. This act is a form of defiance against Mr. Sir and the harsh conditions of the camp, as Stanley is aware that water is scarce and he wants to make a statement about his situation. By discarding the water, he also signals his resistance to the unfair treatment he and the other boys endure at Camp Green Lake.