The mixture is simple and can be double, tripled, etc. I make a double batch and store it in the refrigerator to keep refilling the feeders but only keep this solution for about a week to a week and a half.
Formula is 1 cup of water to 1/4 cup of sugar. Use the microwave to bring water to a boil or your stove top. Let cool and pour into feeders or store in fridge for later use. This is cheaper and better for our seasonal friends.