Thanks. I'm a noob, so all thoughts and experiences are of interestI never put Apple Cider Vinegar in the water. ACV reduces fungus and other organisms from taking up residence in the water(ers). Instead of putting this bitter, vile substance in their water, I dump their water daily and replace it with clean, fresh water (and often put a bit of 'Chick Booster' by Nurovet into the water as a nutritional supplement). It is very important to change the water daily and more important when adding supplements because fungus, bacteria and microorganisms alike all enjoy a bit of extra nutrition.
I've seen people suggesting that their birds won't drink water when they're sick, and later find out that they've added vinegar. Would YOU drink it?
I'm certain that my response is not the popular mantra, but it is exactly how I treat my flock and have done for well over a decade. I will note that in this decade of raising poultry, I have never, not even once had an issue with sour crop. Nor have I had issues with impacted crop and I do regularly 'treat' both my chicken and quail flocks to grass clippings when the gardener comes monthly to 'weed whack' the two foot tall grass down to a height more manageable (I leave the grass long, rake it up, and pile it into a mountain for them to pick through, eating bugs and choice bits of grass and weed along the way). I've had no digestive issues whatsoever with my various flocks, and I've never put vinegar in their water.

I've seen people suggest using ACV for health-purposes (plus reduce smell), although I haven't though about whether the birds mind the taste or not... (I haven't used any ACV though, my quails just hatched)
Maybe it's a bit like fermented feed? Some humans like pickled food, some don't. From what I've heard some birds love fermented food, while others strongly prefers dry. Maybe the same applies to ACV as well? I.e having several water sources where one is with ACV so that they can avoid it if they want, and those who don't mind get the additional health (and smell) benefits?