Carefully cut a small hole in the bottom of the bottle, near to one edge. Note: This is a grownup step. Then, cut a piece of the straw and poke it through the hole. Seal up the hole around the straw with hot glue or packing tape. You want the only path out of the bottle to be down the straw without any other leaks. Safety note: Do NOT try this experiment without the hole for the straw. If there isn’t a way for the gas inside the bottle to escape, the pressure can build up to dangerous levels and cause the bottle to explode.