If you're using frozen sour cherries, defrost and drain them in a sieve at room temperature for at least 1 hour. If you have fresh sour cherries, pit them.
Dissolve the pudding mix in 100 ml of cold water.
In a pot, bring the coconut milk to a boil. Reduce the heat, and pour the pudding mix into the coconut milk while whisking continuously until the pudding starts to thicken. Add the coconut sugar and continue whisking. Turn off the heat once the mix has a creamy, firm consistency.