Crush the nacho cheese chips, reserving 1 whole chip for garnish. Place the chip crumbs on a baking sheet and toast until dark, 5 to 10 minutes; add the sea salt and let cool. Rim a martini glass with agave, then coat the rim of the glass with the chip crumbles.
Add the mezcal, lime juice and Simple Syrup to a cocktail shaker with ice and shake vigorously. Strain into the prepared glass and garnish with the reserved nacho cheese chip.
Combine the sugar and 1 cup water in a small saucepan and bring to a boil. Cook, stirring, until the sugar dissolves. Remove from the heat and let cool completely. Keep covered in the refrigerator up to 1 month.