Begin by hulling the strawberries, removing all green tops and placing the hulled strawberries in a blender along with the cold water. Blend on high speed until the mixture is smooth, for about 30 seconds.

Using a fine-mesh sieve, pour the strawberry mixture into a bowl or pitcher to separate the liquid from the pulp and seeds. Press down gently to extract every drop of juice.

In a large pitcher, combine the strained strawberry liquid with whole milk and sweetened condensed milk. Add additional cold water to achieve desired diluteness. Stir until well-combined.

Cover the pitcher and chill in the refrigerator for at least 1 hour to marry the flavors.

Fill glasses with ice cubes and pour the chilled strawberry agua fresca over the ice before serving.