Peel 3 of the limes, ensuring to remove as much of the white pith as possible to reduce bitterness. Leave 1 lime unpeeled.
Place the limes, sweetened condensed milk, sugar, and water into a blender.
Pulse the mixture 4–6 times. Avoid over-blending to prevent bitterness.
Use a fine mesh strainer to strain the mixture into a pitcher, pressing gently with a spoon to extract the liquid while discarding the pulp and lime skin.
Taste and add more sugar if necessary to balance out any bitterness. Add ice to the pitcher. Serve immediately and enjoy!
Notes
This is best enjoyed fresh but can be stored in the fridge for up to 24 hours.
Mocktail Vibes: Swap out half of the water for sparkling water or club soda.
Cocktail Version: Add a splash of white rum, vodka, or tequila. Start with 1 ounce per glass, taste, and adjust as needed.