Hi James, thank you for that additional information. I am sorry Squirt is not doing well. I will discuss a few possible causes of her symptoms, some of the more common causes, but there are numerous possibilities.
1. Kidney disease- this can explain all of Squirt's symptoms. Kidney disease can be brought on by many different things. Urinary infections, urinary tract stones, congenital kidney abnormalities, and ingestion of particular household items toxic to cats (medications, plants- in particular lilies, antifreeze, grapes, raisins) can all cause kidney injury and lead to kidney failure in cats. Once kidney disease has progressed to kidney failure, uremia develops which can cause the foul odor from the mouth as well as painful sores and ulceration in the mouth. Once in kidney failure, thirst and urination become excessive. The kidneys cannot hold on to water and excessive amounts of urine are expelled, resulting in dehydration.
2. The next possibility is diabetes. Diabetes causes excessive thirst and urination due to high amounts of sugar in the bloodstream.
3. Severe dental disease/ abscessed teeth. This will cause a foul odor from the mouth, drooling, and loss of appetite.
Squirt sounds very ill. My recommendation is to bring her in ASAP (ideally today) to he veterinarian. They will be able to examine her and perform the blood and urine tests necessary to diagnose what may be causing her illness. It does sound as though she may require a stay in the hospital in order to be able to provide her with IV fluids and medications.
I hope this has helped. Please let me know if I can be of any further assistance. I hope everything turns out for the best for Squirt!