Place sweetened condensed milk and cranberry juice in blender; blend until smooth.
Add berries. Blend on low to chop fruit, then blend on high to finish.
Pour 1 1/2 cups of prepared smoothie into 16-ounce glass. Serve immediately.
Turn off blender and stir from the bottom up with a large metal spoon to facilitate blending of frozen fruit. For a lighter consistency, add 1 cup ice cubes (per serving) when blending sweetened condensed milk and cranberry juice.