In a pitcher, combine the cold water and sugar very well and chill until ready to use. You can even do this ahead of time.

Wash limes thoroughly with water and a little liquid dish soap. The soap is needed to get the wax and pesticides off of the limes.

Cut the ends off of each lime and cut each lime into 8ths. Place 1/2 of the limes in a blender.

Add 1/2 of the sugar water,to the blender. Cover and pulse 5 times.

Place a fine-mesh strainer over another pitcher and pour the blended mixture through the strainer and into the pitcher. Use a spoon to press the mixture to get all of the liquid into the pitcher. Dispose of what is left in the strainer. Repeat with remaining limes and sugar water.

Add sweetened condensed milk to the mixture and stir to combine. Taste the drink and add more sugar if needed.

Serve immediately over ice. Serves 4.