Sugar is a natural humectant, meaning it draws moisture from the environment into the skin. So when you apply products with sugar or sugar derivatives, they'll actually help hydrate your skin and keep moisture within.
Secondly, sugar is a natural source of glycolic acid, an alpha hydroxy acid (AHA) that penetrates the skin and breaks down the "glue" that bonds skin cells, encouraging cell turnover and generating fresher, younger-looking skin. Glycolic acid is typically used to treat sun-damaged and aging skin. Because it can be irritating to certain skin types, over-the-counter products typically contain less than a 10 percent concentration of glycolic acid in their formulas.
Sugar's small particles make an excellent topical exfoliant, and are used in a number of body scrubs to exfoliate dead surface skin cells and reveal the glowing, healthy-looking skin underneath. Sugar scrubs also have a few benefits over salt scrubs. For one, small sugar granules are generally gentler than salt, which can cause microscopic tears in the skin; two, because of sugar's natural humectants properties, these scrubs are more hydrating than salt scrubs, which can strip skin of natural oils.