Add 4 cups of water and 1 cup sugar to the blender and liquefy until the sugar dilutes.
Place the sweetened water in a jar
Place the chunks of watermelon without skin in the blender. 4 cups at a time. If your watermelon has seeds get rid of them before blending
Pulverize de the watermelon and add it to the jar. Repeat until you have blend half of the Sandia.
Mix all the ingredients together in the jar and taste.
Add more water according to the taste you want to achieve. I usually use another 4 to 6 cups of water
Add 2 cups of ice