I heard that burning fat leads to acetone odor while burning muscles leads to ammonia smell.
Is this true?
How can I distinguish both smells as they are very similar?
It's definitely true, however both metabolic functions can be happening at the same time, different pathways.
From the suggestions I can mention,
Acetone smells like nail polish remover, ammonia is a common household cleaner. So do you smell like you had your nails done (or perhaps your girlfriend did hers) or that you've been cleaning all day? That may help you with your answer.
The traces of these two smells are studied extensively on the patients with diabetes. If curious, can have a look at this article. ACIDOSIS AND ASSOCIATED CONDITIONS