Azteca

In a food processor, process the coconut flakes and salt until fully combined, about 1 minute—the mixture will be light and fluffy. DO AHEAD: Coconut sea salt can be prepared in advance and stored, in an airtight container at room temperature, up to 2 weeks.
In a small saucepan, bring the chiles and distilled or tap water to a boil over high heat. Reduce the heat to moderate and simmer, uncovered, until reduced by half, about 15 minutes. DO AHEAD: Chile elixir can be prepared in advance and refrigerated up to 2 weeks.
In a small saucepan, bring the vanilla and distilled or tap water to a boil over high heat. Reduce the heat to moderately low and simmer, uncovered, until reduced by half—note that this reduces very quickly, in about 5 minutes. DO AHEAD: Vanilla elixir can be prepared in advance and refrigerated up to 2 weeks.
Pour the lime juice onto a small plate and spread the coconut sea salt on a second small plate. Dip the rim of a 12-ounce glass into the lime juice, then dip it into the coconut sea salt to lightly coat.
In a cocktail shaker, combine the cocoa powder, chile elixir, vanilla elixir, and simple syrup. Shake vigorously until well combined. Add ice to the prepared glasses, then strain the Azteca into each glass. Add enough soda water to fill each glass, then stir to incorporate.