Stir the water, lemon zest, lime zest, orange zest, cinnamon sticks, dried orange peel, whole coriander seed, and nutmeg together in a large saucepan over medium heat.
Stir in the sugar and bring to a boil.
Continue stirring for a few minutes until the sugar dissolves.
Remove syrup from the heat.
Add the lemon juice, lime juice, orange juice, browning sauce, and vanilla extract to the saucepan mixture and stir.
Let mixture cool, then use a fine mesh strainer and strain syrup into a mason jar or other sealable bottle for storage.
To make one cola drink: Combine ¼th-½ cup of the cola syrup with about 2 cups of seltzer water, depending on how strong/sweet you want it. Taste it and see if you want more or less syrup.
Add ice and enjoy! This will stay good in the fridge for up to 1 month.
