Start with the good stuff. In a large cup, add your chopped lemon, blueberries, and sugar (if using).
Muddle it up. Use a muddler or the back of a spoon to mash everything together and release all those juicy flavors.
Get creamy. Pour in the sweetened condensed milk and give it a little stir.
Cool it down. Fill the cup with lots of ice.
Top it off. Add cold water to fill the cup to the top.
Shake it up! Pop on a lid and give it a really good shake. Watch the color transform—this is the fun part!
Punch in a straw and enjoy your pretty pink refresher!