Cherry,
Those little fruit flies seem to like wet along with their fruit and veg so maybe things are a bit wet and maybe acidic with apples turning to cider turning to apple vinegar.
I don’t know the bags you mean. I would sprinkle the bags out onto my big heaps and disperse it with quite a bit of straw to get it drier and air into it.
If the fruit flies are living in it then it has nutrients and bacteria food worth saving.
My 2p worth
