We weighed different sizes of empty bottles from 3 different manufacturers / brands to see which bottle size uses the least plastic and delivers the most amount of water. Here are the results.
We thought that the largest sized bottle would actually use the least plastic for the most amount of water because a larger bottle would hold more water using less plastic than a number of smaller bottles holding the same amount of water. After seeing the results, we realized that a larger sized bottle needs more plastic to be hard enough to hold a larger amount of water, since the fl. oz of water delivered per plastic oz is less. From this limited test, it appears that 16.9 fl. oz is the best. This is likely because it is a size that can have thinner plastic. It is also consumed most frequently and is likely where manufacturers are trying to save the amount of plastic used. Now, we can conclude that the 16.9 fl oz bottle uses the least plastic and holds the most water!