[header] How to make a tornado in a bottle [title] Fill a plastic bottle with water. [step] Leave two inches of air at the top of the bottle. The size of the bottle doesn't matter-but the bigger the bottle, the bigger the tornado. 
The bigger the tornado, the easier it will be to observe the effects on the water. [substeps] If you are only making a one-bottle tornado, you can use a plastic water bottle or a clear glass canning jar.