My son's project tested how would a plants would do being fed salt water, sugar water, and water. In summary, the salt water killed the plants overnight, and the sugar water plants slowly died.
A girl in my son's class did a similar experience except she tested water, diet coke, and sprite. Her results varied from my son's - The sprite and normal water plants died. The only ones that lived were the diet coke plants.
Draw your own conclusions.