In a blender, combine frozen mango, mango nectar, chamoy sauce, Tajín seasoning, and lime juice.
Blend until smooth and slushy.
Dip the rim of your serving glass in chamoy and then coat with Tajín.
Fill the glass halfway with ice and pour in the mango mixture.
Top with sparkling water or lemon-lime soda for fizz.
Garnish with fresh mango or lime slices if desired. Serve immediately.