Sugar water bad for hummingbirds?

I have been feeding hummingbirds for years and use the sugar water recipe from Bird's and Bloom's which is 1 cup water and 1/4 cup sugar and definitely no food coloring.

Hummingbird researchers recommend the table sugar - water ratio you use to feed them since table sugar closely resembles nectar. No coloring. You are just fine to do what you are doing.

It can be bad for them if it's not kept contaminant-free. (Source)

Cleanliness

Sugar water is a very rich growth medium. Yeasts like to eat it causing fermentation which can harm hummingbirds. Mold and bacteria grow in it and can also harm the birds. That is why it is important to keep the feeder clean and the nectar fresh. You must change the nectar frequently to avoid these contaminants. In cooler temperatures we recommend changing it every seven days. If the temperatures are getting above 70 degrees, follow this chart:

Remember: these are guidelines, not absolutes. If you notice that the nectar is turning milky or that white strings or black spots are growing in it, change it more often. Clean the feeder with very hot water each time you refill it. Most good feeders,and all of of the ones that we sell, come apart for easier cleaning. Be sure and take them apart every time. It is usually the work of a couple of seconds. If contamination occurs, use a mild bleach solution to sterilize it, but if you use bleach, rinse thoroughly afterwards. Even a tiny amount of bleach could be harmful to birds weighing only a quarter of an ounce! Glass or metal pieces can be boiled, but you should probably not boil plastic pieces. The black mold may leave a very faint stain, but this will not affect the safe operation of the feeder.

I agree that health issues for the hummingbirds exist when the sugar water is not changed often, and the feeder is dirty. Regardless of temperature, I change the food and clean the feeder every 3 days.

While we do get hummingbirds at our feeder, we also get chickadees, which I find surprising. At first I thought they were just checking out a new feeder they hadn't seen before, realizing it's not seeds, and giving up in disappointment; but no, they stay and drink. They do know it's not a seed feeder and they stop by anyway.

As long as what you feed the hummingbirds is fresh, you're fine. Most hummers carry a fungus, and they are the ones who foul the nectar. It doesn't matter if it's sugar water, or store bought nectar. I've fed hummingbirds for 20 plus years, always have around 20 of them, at least, who feed on a regular basis. I use sugar water. I think that myth is promoted by the companies who sell nectar.

I've heard of many people that use sugar water, but not sure of it's effects. Personally, I purchase nectar because it is fortified with nutrients. In the PNW where I live I feed them all year because we have a species that stays during the winter.

lawdy, something else to worry about while I'm trying to be kind and nice. Have done the same thing for years. all seems fine HOWEVER, a few days ago we seem to have a bully (think I'd mentioned before) then I noticed a female, rather plump, and spastic. I wondered, is my solution okay (YES) or is there something wrong with her (maybe) was the bully making things uneasy for other feeders? The poor female drank (used to drink on very very quick sips/retreat/sip/retreat/sip,,,,felt sorry for her. attributed it to the bully, she'd look around before and after a sip. she also even 'poked' at the glass with the red water inside. It's been fine for years, now what do I have to worry about. I'm sure I'll hear it all from here no offense