Start by adding the raisins, apricots, hibiscus, and tamarind to a medium sized saucepan over medium heat, then pour in 3 1/4 cups of water. Let this come to a simmer, then once it reaches a simmer, let cook for 5 minutes. Remove from heat and let cool.
Use a slotted spoon to remove the tamarind, then press it through a strainer into the blender, then discard the seeds. Transfer the rest of the fruits and liquid from the saucepan into the blender, then bled for 30 seconds, until smooth. Strain this mixture back into the saucepan.
Once you’ve strained the fruit mixture back into the saucepan, whisk in the sugar, tajin, and lime juice, then set over medium heat. Once the sauce comes to a simmer, let the sauce reduce for 30 minutes, stirring occasionally.
After 30 minutes, the sauce should be slightly thickened, and will finish thickening as it cools. Store in the fridge, and let sit at room temp for 30 minutes before using.
Start by blending together the cucumber, lime juice 1/2 cup water and agave nectar. Strain into a 2 cup measuring cup.
To assemble the drinks, dip 4 tall glasses into the chamoy rim sauce, then add about 1/2 cup of ice to each glass. Divide the cucumber mixture between the glasses, then top with seltzer. Give it a stir, then garnish with a cucumber slice.