Add ice to a cocktail shaker.
Add 1 shot (1½ oz) tequila to the cocktail shaker.
Squeeze 1½ limes into the cocktail shaker.
Shake vigorously for 30 seconds.
Strain the drink into a lowball cocktail glass filled with ice.
Top with a splash of Topo Chico.
Optional: Garnish with a lime wedge.