Place the sugar, salt, and cocoa powder into a saucepan and whisk to break up any lumps in the cocoa powder.
Add the water to the saucepan and stir to moisten the dry ingredients.
Place on the stove over medium to medium-high heat and stir to dissolve the sugar.
Bring the mixture to a boil and boil for 4 minutes.
Remove from the heat and stir in the vanilla.
Add the syrup to a clean container and store in the refrigerator.