Sugar absorbs water much like salt, and can prevent plant roots from absorbing the water. Sugary drinks can also throw off the nitrile balance, hindering plant growth significantly. While water is the best choice, Coke, Sprite and apple juice will affect plants differently.
Classic Coca-Cola contains a whopping 3.38 grams of sugar per ounce, making the carbonated treat nearly toxic to plants, which will be unable to absorb the water and nutrients necessary for growth. Variations on the classic such as Coke 0, Coca-Cola C2 and Coke Blak contain little to no sugar, but offer no additional benefits over water.
At 3.25 grams of sugar per ounce, Sprite rivals Coke in its sugar content and toxicity to plants. However, Sprite does have the surprising benefit of keeping cut flowers and plants fresh for a lot longer than than water, as do many other clear sodas. When keeping cut flowers, they can be added to a vase of pure Sprite for best results.
Apple juice sugar content varies from brands to brand, but all-natural apple juice with no sugar added will have little negative effect on growing plants. Because apples do naturally contain sugar, apple juice is still less effective than water for plants.