Why does my vaginal discharge have a sweet smell?

See a Gynecologist: A sweet smell can be caused by sugar in your urine, glucosuria, which could occur if you have developed diabetes. Some personal lubricants like Astroglide, have sugars in them, glycerine, which is sweet in taste. The most common odor in a vaginal discharge is a fishy smell caused by bacterial vaginosis. Other diseases like Maple syrup urine disease are very rare.