Just as Mary Poppins sang that "a spoonful of sugar helps the medicine go down," a little sugar can help plants recover faster from a lack of water or heat stress. Nutrients in the sugar help plants build back their own energy, and just a spoonful of sugar in the watering can may even help save the life of a dying plant.
Mix 2 teaspoons of white granulated sugar with 2 cups of water. Stir until the sugar has been dissolved.
Place the distressed potted plant in the sink. If the distressed plant happens to be planted in the ground outside, leave it where it is.
Slowly pour the sugar water over the plant, being careful to touch every leaf and flower. Let the sugar water drip down and soak into the ground, saturating the roots, as well. Plants don't just absorb nutrients through their roots--they also absorb them through their leaves, and for a severely distressed plants, you need to cover both bases.
Let the plant sit for two days and then repeat the process. Continue watering with sugar water every other day, or three times a week, until the plant recovers. You'll know when the plant is feeling better by its color and when its leaves grow rigid again. After that, continue to water, just without sugar.