100g sugar
2 tablets activated charcoal

You need to grind the charcoal and melt the sugar. Mix the two. When the sugar is melted, pour onto a silicone mat and cool. Pulverize the sugar in the blender and use it according to your taste.

After grinding, the formerly all-black mass will turn gray. You can still add activated charcoal in the mortar, but it won't be completely black. For me, however, it is also sufficient in gray.

If you use the black sugar for glass rims in coctails, then it becomes black again by the lemon juice or whatever you use.