Have you tried making apple cider vinegar? It tastes great and has heaps of uses. I use damaged and windfall apples from under our tree, but it can also be made from apple peels and cores. You don’t need a large amount – the peels and cores of six apples will make a jar of vinegar. And if your tap water is chlorinated, you can boil it for 30 minutes to get rid of the chlorine.
If you only have time to try one fermenting project, I suggest you make it this one: it is so ridiculously easy as well as satisfying to make something so useful from scraps that you'd normally chuck on the compost. I followed these instructions: https://wellnessmama.com/124169/make-apple-cider-vinegar/