Why does the urine sometimes smell sour?

Sour like vinegar?: Haven't heard of urine smelling sour like vinegar. Urine can smell stronger (more ammonia / urea odor) if one isn't drinking enough water. It can smell like ketones during fasting or certain medical problems. Some foods give urine odd aromas, such as after eating asparagus. A primary care doctor can evaluate if one keeps having such aroma symptoms, to rule out urine infection, and look for causes.