Step 1

Stir together 7 cups cold water with 3/4 cup sugar and set aside.

Step 2

Add 1 Tbsp lime zest add juice from 5 limes into your blender jar (it's super fast to juice limes if you have a citrus squeezer like this one). Pour 3 cups of your sugar water into the blender (I only add 3 cups at this time so my blender doesn't splash all over the place).

Step 3

Add 1/2 cup sweetened condensed milk. Blend until smooth and frothy. Stir in remaining sugar water and serve over ice.