I think cider vinegar is just a tonic, I've never heard it being an effective wormer.
As for stuff in the water, I don't think it's any more reliable than food to be honest. They will still vary in how much they drink, or find water elsewhere.
What I do find helps is Marriage's premixed food containing flubenvet - takes the hassle and error out of me trying to mix small amounts of powder into layers pellets.