|MadSci Network: Botany|
Watering a plant with sugar water will usually harm it because it makes soil water less available to the plant. In technical terms, it lowers the water potential of the soil water by lowering the osmotic potential. Water flows from higher to lower water potential. The water potential in the plant must be lower than the soil water potential in order for water to flow from the soil into the plant. Plant roots are not adapted to absorb sugar. Plants make all the sugars they require via photosynthesis. Plant water relations are discussed in college introductory botany texts, plant physiology texts or soil science texts.
Try the links in the MadSci Library for more information on Botany.