The most direct result is water leaving the cell. The cell membrane is semipermeable, which means that only certain chemicals can pass through it. Water can pass through it but sugar cannot. This results a difference in concentration of sugar between either side of the membrane. Water has the tendency to balance out this difference and will move to the side with higher concentration. As a result, water leaves the cell. If the difference is large enough, the cell membrane can detach from the cell wall in a process called plasmolysis.

On the surface of the cell membrane, there are proteins that transport the sugar molecule into the cell. Therefore, it is possible for the root to gather nutrients from the sugar water. However, sugar water will attract bacteria, fungi, and insects, which could be harmful to the plant.

Sugar absorbs water. This means that dumping sugar-laded water on plants will mean that the plants can't extract the water out of the sugar for their own use, and plants need water to extract nutrients from the ground and to draw in carbon dioxide from the air. Thus, despite the fact that plants use sugar in their own cells as an energy reserve, sugar in the soil will poison them.

How sugar water affects a plant will depend on how well the plant is doing. For a healthy plant, sugar water may cause the plant to die. For an unhealthy plant, sugar water may help bring the plant back to health. The type of plant will also matter. It would be interesting to do an experiment with sugar water and plants. For an experiment like this, refer to this site for a plan.