In the Field Trip episode where the twins go to a museum with their class. One of them brings 1 can of soda. Shortly that can of soda is dropped on the ground. The teacher yells at them. Well, there was only one can of soda, and clearly no other can was in either girls hands. The last shot before they walk off, one of the twins is holding a can of soda in her hand, a can that was not there in previous shots for the scene, yet there was still a can of soda on the ground when they left with the can a of soda in their hand.

Where did the other can of soda come from?