Don’t use the fruit juice in your feeder to attract the birds. Birds just need a simple white sugar solution 1:4 ratio with water which perfectly matched with natural flower nectar. When you use the juice in your feeder the other unwanted audience like bees and ants are more active, they like it too much as compared to normal nectar. And in the presence of bees and ants the hummingbirds can’t feed properly. Sometimes the bees and ants mix with nectar which is very harmful for birds.
Actually sometimes the fruits are acidic. Moreover the fruit juice contains fructose as compared to sucrose found in natural flowers. Both are similar but not the same which is sometimes harmful effects on birds so we are strict to use simple nectar.