Most authorities insist that sugar water should be kept in the refrigerator because it provides such a rich environment for breeding mold and bacteria. However, the experts differ on how long it can safely be stored. Domino Sugar claims that sugar water can be safely kept in the fridge for two weeks, but the Audubon Society suggests that it be discarded after one week.

On the Other: Sugar water can be unrefrigerated

In a recent piece on the care of hummingbirds, Cornell University claims that sugar water can be safely left in a hummingbird feeder for an entire week. They note that the possibility of mold and bacteria growth can be prevented by simply washing the feeder every seven days with soap and warm water, then rinsing thoroughly. Cornell, however, does not comment on the safety of the unrefrigerated mixture for human consumption.

Bottom Line

Better safe than sorry. Since there does not seem to be a consensus on how long sugar water remains safe, it's best to make it in small batches so that you only use it up as quickly as possible. The recipe is simple to make, one part sugar to four parts warm water, stir until dissolved. And it's simple to recalculate, since whether you're using teaspoons, cups or quarts, the measurements are still the same. Just make it fresh each time you need it, and use up the leftover as soon as you can.

Source:

Once a week change sugar water

Domino sugar two weeks

Audubon says one week

More Information:

Making a sugar water nectar for hummingbirds