What is a negative externality of drinking a can of caffeine-free, diet soda?

A negative externality are the ones who suffers and serves as a third party from which they are being affected because of stimulus or both of the first and second party. This will likely cause resources and economy to be affected. By this, in the given sentence above, the drinking of can and caffeine free, diet soda, would likely cause a negative effect in the economy for if the cans used and bottles are not recycled and are not dispose of properly, it will take up the land fill, making it hard to dispose of these cans and bottles, thus, it destroys also the environment.