What is the best recipe for making DIY hummingbird nectar?

The simplest recipe is 4 cups of water and 1 cup of white sugar, which are heated up to dissolve the sugar then cooled. You do not need to add red dye, in fact, that can sometimes be harmful for the hummingbirds. Same receipe as here: https://nationalzoo.si.edu/migratory-birds/hummingbird-nectar-recipe