I am not an expert but I will share my experience...
When my brother was in hospital 2 weeks ago I said to him "your breath smells like pear drops" (the sweet) and the doctor was there and explained it to me. But I don't wanna get it mixed up, so I have copied this from a diabetes booklet from the NHS.
"This 'fruity' 'sweet' odor can be a sign of hyperglycemia (excessive blood sugar) and ketoacidosis, a buildup of ketones (acid) in the blood. Ketoacidosis, which occurs mainly in people with Type 1, or juvenile diabetes, requires immediate care.