In a medium saucepan, combine equal parts sugar and water. Place over medium heat, stirring until the sugar is fully dissolved, about 2–3 minutes.

Once the sugar has dissolved, reduce the heat slightly and add cacao powder, stirring thoroughly until fully incorporated.

Raise the heat to medium-high and bring the mixture to a steady boil, stirring constantly for about 3 minutes.

Remove the saucepan from heat and stir in the vanilla extract. Let the syrup cool in the pan for about 5 minutes.

Transfer the cooled syrup to an airtight container and store it in the refrigerator.