What is the best way to clean Hummingbird feeders? How often should a feeder be cleaned?

During hot times of the year, clean and change nectar every 2-3 days. In more mild weather (60s/70s), every 6-7 days. If you start to see the nectar getting cloudy, you should wash out the feeder and change the nectar to be fresh. Clean hummingbird feeders with hot water and distilled vinegar. Brush it around, rinse thoroughly, let it dry, and fill with nectar. No need to fill your feeder always to the top as you're wasting the sugar water. Fill about 1/3 of the way up.