1 lemon, juiced
1/2 - 1 frozen banana, chopped
1/4 cup sugar, or to taste
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.