1 C sugar
6 C cold water
1/3 C sweetened condensed milk
Mix cold water and sugar very well and chill until ready to use. Mix cold water and sugar very well and chill until ready to use. Wash limes thoroughly with soap. Cut the ends off the limes and cut each lime into eighths.
Place half of the limes in your blender. Add half of the sugar and water, pulse in blender until well blended.
Place a fine-mesh strainer over a pitcher and pour mixture. Dump the pulp and residue in the strainer into the trash. Repeat with remaining limes and sugar water.
Whisk in sweetened condensed milk.
Serve immediately with ice.