1 lemon, juiced
1/2 - 1 frozen banana, chopped
1/4 cup sugar, or to taste
Cold water
1) Add lemon juice, banana, sugar and water to blender. Adjust water according to how thick you want your drink to be. Blend and voila, a refreshing, zingy juice!
I do this when I'm craving juice and have none in the house, since I always have frozen bananas and lemons.