Remove the hummingbird feeder, and pour any remaining sugar water down the drain.
Fill a bucket with hot water, and then add the bleach.
Set the hummingbird feeder parts in the bucket, and let them sit in the solution for one hour.
Use a bottle scrubber to get rid of any mold or dirt that was in the hummingbird feeder.
Let the hummingbird feeder air-dry. The bleach will evaporate without leaving a film; this is perfectly safe for your hummingbirds. Once the hummingbird feeder is clean, fill it with a fresh batch of sugar water.
Repeat whenever you notice the liquid in the hummingbird feeder become cloudy, or if you see black mold growth.