Simple syrup stored in the fridge generally lasts about 2 weeks to 1 month depending on the sugar-to-water ratio and whether it is flavored or plain. A standard simple syrup (1:1 sugar to water) lasts about 2 weeks to a month when refrigerated in an airtight container. A richer syrup (2:1 sugar to water) can last up to 6 months under the same storage conditions. Flavored syrups or those with added fresh ingredients tend to have a shorter shelf life, usually about 1-2 weeks. Signs that simple syrup has gone bad include cloudiness, off smell, or mold growth.
