I'm going to make some assumptions about what's going on here because to answer fully, I would need more info. Sugar crystals form out of water when the water becomes "supersaturated." This means that water can hold a certain amount of sugar, and any sugar above that can't be dissolved in water. When all the sugar that water can hold is dissolved, this is "saturated," and when there is too much and it comes out to form crystals, it is "supersaturated." The time for sugar crystals to form depends on how much supersaturation there is--meaning more sugar lets crystals form faster.