Combine ice, margarita mix, tequila, and mango nectar in a blender; squeeze 1 lime half into the blender. Blend until cocktail is smooth.
Cut remaining lime half into wedges. Pour 1/4 to 1/2 inch of sugar onto a small, shallow plate. Moisten rims of 4 glasses with a wedge of lime, dip the moistened glasses into sugar. Pour cocktail into the prepared glasses.
