It's acetone breath, it is a temporary side effect of keto-adaptation. Other ones include excessive thirst, light headedness and headaches.

Most people never heavily use ketones, so it takes the body some time to re-build the machinery to do so.

Yeah, the symptoms sound like detoxication, those generally having foul smells and needing extra water to wash away our old fears.

I confirm I did have all of the above. Possibly the light-headedness was also cause by not having eaten enough, but it was too strong for that to be the only factor.

as mentioned in the article-- It's acetone, not ammonia.

Acetone is one of the byproducts of keto metabolism, and, unlike other byproducts which are expelled in the urine, acetone is breathed out, resulting in the slightly-sweet-smelling "keto breath".