I know all mammals can for sure.
I would thing any animal that uses insulin can potentiality go into a diabetic coma.
So if reptiles produce insulin then yes a coma is a thing that could happen...
Since animal diets are different that ours and more "natural", it's way less likely to happen, seeing as most animals do not stuff their face with white sugar. But it could be more predominant amongst animals that live off our garbage? Just a personal thought.
In these cases, the animal would most likely die, unless treated ASAP.
as far as a coma from something else, I have no idea