Mix chili powder and sugar on a small plate, moisten the rim of a copper mug or highball glass with lime juice, and dip into the chili-sugar mixture.

Fill the prepared mug with ice cubes and add the mango juice, lime juice, and simple syrup.

Stir gently to combine all ingredients, then top with ginger beer.

Garnish with a fresh mango slice and lime wedge on the rim and serve immediately with a straw.