Sugar dissolves in water faster than salt due to its different chemical properties. Both substances are similarly sized hard crystals, but their molecular and bonding structures are different, and they react differently when combined with water.
Salt is a compound of sodium and chloride, and the molecular ionic bond that joins these particles together is very strong. Table sugar is composed of glucose and fructose molecules, but the positive-negative bond is weaker between these components. When dissolved, sugar molecules have more opportunities to bond with positive-negative water molecules. Therefore, sugar dissolves faster than salt, because its component molecules are more soluble in water.