Combine sugar and water in a medium sauce pan. Heat on medium until sugar is completely dissolved. Note: Sauce will bubble, so pan must be larger than quantity would normally dictate.
Once sugar is dissolved, add cacao powder. Stir until thoroughly combined.
Bring mixture to steady boil.
Stir constantly and boil for 3 minutes.
Removed from heat and add vanilla.
Allow to cool and then transfer the syrup into the container of your choice.
Notes
You can use honey or maple syrup in place of the sugar at a 1:1 ratio.