G.B.
How odd that it is sweet smelling. That is often a tell tale sign of blood sugar levels in an adult. When I was training to do EMT work that was something I remember from the class.
For instance one might come upon a person who is unconscious and they have on a diabetic warning bracelet.
If their breath smells sweet/fruity (Hypoglycemia) we did one thing and if it smelled like acetone/fingernail polish (Hyperglycemia) remover we did something else. One was to rub sugar, like pop or OJ in their mouth, not enough to choke them but that some sugar could be absorbed through the mucus membranes.
Of course there would be other symptoms of either illness in this case, just stating that those are the only times I know of that saliva smell tells some something important.
I would ask the doc for sure about his one. He may want to rule out juvenile diabetes.