Glass hummingbird feeders are designed with a tank and several small holes near the bottom where hummingbirds can feed. Inside is sugar water, usually dyed red, which is a color that hummingbirds are attracted to. Hummingbird feeders need to be cleaned regularly to keep them healthy for the hummingbirds and free from mildew. If possible, clean and return your feeder back in place within a day or two to ensure the hummingbirds return quickly.
Rinse the hummingbird feeder out before each refilling. Hot tap water will suffice. Do not use soap, which, if any accidental residue is left, will deter the hummingbirds from drinking from the feeder.
Soak your glass hummingbird feeder in bleach water about once a month. In the meantime, inspect your feeder, at least weekly, for mold. If you spot any, soak in bleach water immediately rather than waiting. Use a quarter cup per gallon of water and let the feeder soak for an hour. Be sure it is completely submerged.
Rinse thoroughly and fill it back up with syrup, which is one part sugar cane and four parts water. Some people boil the water first and allow it to cool to prevent fermentation, but this is not necessary. Add some red dye, if desired. This is also not necessary, but you might have more hummingbirds come to your feeder.
Carefully carry your hummingbird feeder outside and set it back on its hook. Enjoy the hummingbirds, which should be back eating from your feeder within a day or two.