Baking soda or baking soda and vinegar is what dissolves coffee residue.
When you need to clean coffee residue up from a coffee cup or coffee maker you can use baking soda and water or baking soda and vinegar diluted in water.
You can descale your coffee maker and remove coffee residue from inside the coffee maker by mixing some baking soda with some water and then run the coffee maker through a brew cycle.
Commercial coffee descale solutions also work well for getting rid of coffee residue and descaling of the coffee machine.
You can also remove burnt coffee from the bottom of a coffee pot by using the vinegar and baking soda solution.
Allow the coffee pot to sit with a mixture of vinegar and baking soda and allow it to fizz and then scrub the coffee pot with a sponge or scrub brush.
Then rinse the coffee pot out.
You can also remove dried coffee stains by mixing together a tablespoon of white vinegar and washing up liquid with two cups of water.
Sponge this mixture onto the stain and keep blotting it with a white cloth or paper towel until it comes off completely.
Dry the area with a dryer or a fan.