The keto diet is ketosis
If you’re on a low-carb, high-fat ketogenic (keto) diet, your body goes into a state of ketosis, where it burns fat instead of carbs for energy. During this process, ketones are released and excreted in the urine, which produces a fruity or acetone-like odor. This odor is usually harmless and a common side effect of ketosis. However, if the smell is very strong or unpleasant, it is worth monitoring your diet and hydration level.

Maple syrup urine disease (MSUD)
Maple syrup urine disease is a rare genetic disorder in which the body is unable to break down certain amino acids. As a result, the urine has a strong, sweet smell similar to maple syrup. This condition is usually diagnosed in infancy and can lead to serious health problems if left untreated. However, in very rare cases, adults with a mild form may develop symptoms later. If your urine smells like maple syrup and you feel generally unwell, see your doctor.

Bladder fistula
A bladder fistula is an abnormal connection between the bladder and another organ, usually the bowel. This causes intestinal bacteria to mix with the urine, creating a strong, foul smell similar to feces. Other symptoms of a bladder fistula may include a urinary tract infection, cloudy urine, and pain during urination. Bladder fistulas are serious conditions that require medical treatment and often surgery.