This is my go-to recipe for decorating cookies and cakes; it works wonderfully and has a beautiful smooth finish. Add food coloring or flavoring if desired.
Beat sugar and egg whites in a large bowl using an electric mixer on low speed until evenly combined and shiny, about 3 minutes. Add the water gradually, beating on medium-high until icing is smooth and the desired consistency, about 5 minutes.
Per Serving: 74 calories; protein 0.3g; carbohydrates 18.6g; sodium 4.9mg.