Water icing is simple and cheap to make. It’s also super flexible, suitable for many sweet treats!
Sift the sugar into a bowl. Decide what optional flavourings you are going to add, if any, and have them to hand.
Stir in the hot water until the icing is a little thicker than you want it to be. Add in any of the optional flavourings you want, then recheck the consistency. Add a little more hot water at a time, if needed, until it reaches the right consistency. Allow to rest for 30 minutes before use.
What do I mean “right consistency”? It depends on what you want it for. A drizzle on icing would need to be more liquid, icing for cinnamon rolls would be a little thicker. If in doubt make it a little thicker than you think it needs to be, try it on a small sample, then tweak the thickness as necessary.