Rumors that Pepsi, apple juice and other sugary beverages can help promote plant growth have long circulated around the Internet. The truth is that any sugary drink will do far more harm than good if they are used to "water" plants.
Pepsi, or any other sugared cola, will not help a plant grow.; instead, it will do the opposite. If you "water" a plant with any sugared beverage, you will actually harm it. In a message posted by Botanist David Hershey on MadSci website, he says that plants are not adapted to absorb sugar, and it makes it harder for plants to absorb water already in the soil.
Many store-bought apple juices have sugar added to them for taste, so they're just as bad for plants as Pepsi or any other cola product. Even natural apple juice has sugar in it, so while it may not be as bad for the plants as Pepsi or other cola, it certainly is not good for the plant and will not promote accelerated plant growth.
In nature, plants survive on water and sunlight. If you're keeping plants indoors or outdoors, regular water should do a good job of keeping your plants alive and healthy.