From "Maximum Yield" magazine (November-December 2007), article titled "Why use sugary supplements?": "Simply put, flowering plants are burning these carbs trying to make large fruit or vegetables, or big beautiful blooms, faster a marathon runner trying to win a race. Not to mention that the process of photosynthesis, which produces the sugars, takes a lot of energy. By adding one of the organic carbohydrate supplements (molasses, sugar, etc.) to your nutrient solution the carbohydrates that have been allocated to the flowering process will be replenished more easily. This will save your plant the energy it would need to create those sugars itself, and your plant can focus more of its energy on the flowering process.
**NOTE: i dont think its recommended for hydro because of root rot**