The simplest way to mix the apple peel powder using only a spoon is to make a slurry. It's an essential and simple technique used for mixing ingredients when baking/cooking to prevent clumping.
Start with just a tiny amount of water (or whatever) in a glass. Add the apple peel powder. Stir it into a thick paste. Gradually stir in small amounts of liquid until it's no longer a paste. Add desired amount of liquid, the rest of your stack, etc., stir. Enjoy not having the apple peel powder all floating at the top in a bunch of clumps.