I never knew bike water bottles were called 'bidons'. You learn something new every day... When I glanced at this thread on my phone I thought people were advocating washing them out in the bidet! Ewww!
I personally use, erm, SIS 'bidons' and just wash them with hot soapy water, rinse well and allow to dry. Not saying that's best but I've not been ill through it and I usually have SIS electrolyte in there in summer, so not just water.
My Camelbak also gets filled with juice if I'm off-roading. This then gets rinsed out afterwards with plain water and kept in the freezer, which seems to be good at preventing nasties from forming inside.
I don't even want to think of animal poop on my bidet or bidon or indeed anywhere.