Apple Cider Vinegar does remove and clean up calcium deposits and it works great for cleaning coffee makers as well as shower heads and anything else that needs calcium deposits removed.
Straight white vinegar works great too for cleaning calcium deposits but you certainly can use Apple Cider Vinegar for the same thing if you want too or if that' all you have on hand.
If you need to clean a shower head you can pour some Apple Cider Vinegar into a plastic bag and then tie the bag around the shower head to allow the shower head to soak in the Apple Cider Vinegar and it will clean the calcium deposits from the shower head.
Or you can remove the shower head and soak it in a bowl or container of Apple Cider Vinegar as well.
For coffee makers just pour a bit of Apple Cider Vinegar into the water reservoir and run the coffee maker through a complete cycle.
Then run some straight water through the coffee maker to clean the Apple Cider Vinegar out of the coffee maker.