Wash the apples well and put them in a jar.
Brew mustard powder in a small amount of water. Add honey and salt, dissolve in water. Pour apples with a warm solution, try to crush something with a glass, for example, and cover with a plastic lid.
Leave the apples for a week at room temperature until they begin to wander (bubbles appear), in the first days the apples absorb the solution, then just add water so that they beat completely covered.
Then put the pickled apples in the jars in a cool place for a month, after which they can be eaten.