Sorry to hear you have a sick chicken. This sounds like one of my chickens almost right after I brought her home.... just a few days later. She had a sour crop. They basically have gotten a clogged up crop and the food stuck in there has started to ferment. Since it hasn't emptied they don't feel hungry so they don't eat any more but they do drink water and that just adds up. At least that's what happened to my bird.
You could bring her to the vet and they will empty it and give you antibiotics. You could also try to do it yourself. You hold her upside down and massage the crop from bottom to top and vomit her. Keep doing this till its empty but give her frequent breaks to breath. The danger here is that she could breath some into her lungs. I think that's what happened to my bird when I tried it because she died that night.
If you do it successfully however, just isolate her from the other birds and make sure she gets ACV water, scrammbled eggs and some greek yoghurt in her, then try and get her to eat real chicken food the next day. You can also just search Sour Crop on this website for advice because I'm fairly new myself. I have just run into every concievable problem you could get with a flock of birds since I've had them haha. And your title said Sour Crop to me instantly!
My advice is that if you want her to survive, just take her to an avian vet and let him/her take care of it but it's your choice and what you're comfortable with!
Good luck!! And let us know how it goes!