For my experiment we need: a bottle, a kettle of hot water, a balloon, cold water to cool the bottle down
Close the neck of an empty bottle with a rubber balloon and then put the bottle into the kettle of hot water. The balloon is gradually inflated. The heated air in the bottle expands and the growing pressure causes the balloon on the neck of the bottle to inflate. Then cool the bottle, reducing the temperature of the air inside the bottle. Colder air has lower pressure. External atmospheric pressure pushes the balloon inside the bottle.