I always wash mine with undiluted white vinegar. I do that every time I refill them, not just after the winter, though.

I use vinegar, also. It rinses clean very quickly, and doesn't leave a residual smell like chlorine bleach or soaps.

I use hot water with just a few drops of dish soap, use a brush for the feeding ports - every time I refill them all year around. I rinse copiously each time.

I use a 2% bleach soak at the end of season and anytime theres a hint of mold. Then rinse them very well with cold water. If there is a bleach residue smell the hummers havent complained nor have their numbers dwindled.

Thank you so much for the correct ways to clean. I cleaned mine, all have been filled and put back up for the season. It wasn't too long that we were rewarded with two little new ones for their first drink at our porch.
Ann in So Ut

I will add that on regular routine cleaning its hot water with a little dish soap , sponge scrubber, port brush for feeder holes and a good cold rinse.

I use dish soap and hot water for my feeders and use the craft wire to clean the ports or any tubing if I use a tube feeder.