In a saucepan over medium heat, warm the coconut water and sugar until the sugar has just dissolved.
Using the flat side of a knife, lightly crack the cardamom pods, but do not remove the seeds. Add the cardamom pods to the coconut water and sugar mixture and heat for 25 minutes at just below a simmer.
Remove the mixture from the heat and cover. Allow the mixture to seep for 15 minutes.
Strain the mixture through a fine mesh sieve and into a storage container.