Gather all your ingredients and ensure your ice cubes are fresh and frozen solid. Having everything measured and ready before blending will ensure a smooth process and the perfect slushy consistency.
Add the ice cubes to your blender first, filling it about halfway. The ice should be standard-sized cubes, not crushed, as they'll blend into the perfect slushy texture.
Pour the cold water over the ice cubes, followed by the blue raspberry syrup. The syrup should cascade over the ice, creating swirls of vibrant blue color that will soon be blended throughout.
Add the granulated sugar, freshly squeezed lemon juice, and vanilla extract to the blender. The lemon juice adds a subtle tartness that balances the sweetness, while the vanilla provides depth to the fruity flavor profile.
If you want that signature bright ocean-blue color, add 2 drops of blue food coloring now. This step is optional but helps achieve that iconic Dunkin' look that makes the drink so visually appealing.
Secure the blender lid tightly and blend on high speed for 45-60 seconds, or until the mixture reaches a smooth, slushy consistency with no large ice chunks remaining. You should hear the sound change from loud crushing to a smoother whirring as the ice breaks down completely.
Stop the blender and check the consistency by giving it a gentle shake. The mixture should be thick enough to hold its shape but still pourable, similar to a frozen slushie. If it's too thick, add 1-2 tablespoons of cold water and pulse a few more times.
Pour the Ocean Coolatta into a tall glass immediately, as it will begin to melt quickly. The drink should have a vibrant blue color and a frosty, icy texture. Serve with a wide straw and enjoy this refreshing tropical treat right away for the best flavor and consistency.
