Well, their urine does. That’s how Hippocrates identified the disease. He dipped his finger in their pee and said, “Oh. Tastes like honey (mellitus)”. But some folks, who also peed a lot, had urine that was, well, bland. Insipid. Hence we also have a diabetes insipidus.
MrRobyn is a type II diabetic (non-insulin dependent) and I can usually tell if his glucose is high if his sweat smells kinda fruity. I haven’t noticed a discernably sweet taste, however.