[header] How to clean a hummingbird feeder [title] Pour out all the nectar. [step] As you likely stock your feeder with nectar, make sure to remove that before cleaning the feeder. You should simply pour the nectar down the drain. 
Once birds have fed in the liquid it will contain mold and other contaminants so do not save unused sugar liquid from inside of the feeders. You can make more nectar later with simple sugar and water or restock the feeder with store-bought nectar.