A good formula for hummingbird food: 4 parts water to 1 part sugar (so 1/4 cup sugar to 1 cup water). The water should not be distilled, just use tap water. The sugar should be white table sugar. Do not use artificial colors (red dye does NOT help attract hummingbirds) or other additives. Never use honey or artificial sweeteners, for to do so may kill the birds. The ingredients can be mixed using cold water.
Any mixture of sugar and water will ferment and can host the growth of mold spores and/or bacteria. Because of this, the mixture must be discarded regularly (if not eaten by the hummingbirds) to avoid these problems. In moderate temperatures, such as 60-85 degrees F. (15-30 degrees C.) a mixture should last about 3 days. It will need to be changed more frequently at higher temperatures and less often at cooler temperatures. Regardless of the mixture's age, discard it immediately if you see cloudiness or you see mold growing in the feeder. Always clean a feeder thoroughly before refilling; do not "top off" a feeder which is low in mixture. Clean with warm water and detergent, and rinse very thoroughly.