The correct answer is the third option, the space that the empty can will take up in a landfill if not recycled properly. If empty cans were not recycled properly, they would take up a lot of space in landfills and won't be able to decompose, since it is made out of aluminum, which would be hard to decompose, therefore the negativity of drinking a caffeine-free soda is the improper disposal of the empty can itself.
