For the syrup, heat the water and sugar in a small saucepan until dissolved. Remove pot from heat, add jalapeño and mint, and let cool.
To a cocktail shaker filled with ice, add 1/2 ounce of syrup along with the tequila, grapefruit juice and lime juice. Shake then strain into an ice-filled rocks glass that has been rimmed with a lime wedge and a mix of pink salt, chili powder and sugar.