Which of the following conditions is characterized by a fruity breath smell?

The condition characterized by a fruity breath smell is hyperglycaemia, which is typically associated with uncontrolled diabetes. When blood sugar levels are significantly elevated, the body starts to break down fats for energy instead of glucose. This process produces ketones, which are released in the urine and can also be exhaled, leading to a distinct sweet or fruity odor on the breath. This phenomenon is often an indication of diabetic ketoacidosis, a serious medical condition that requires immediate attention.

In contrast, fainting, hypoglycaemia, and dehydration do not typically present with fruity breath. Fainting is generally related to a lack of blood flow to the brain, hypoglycaemia results in symptoms like sweating, trembling, and confusion, and dehydration might cause dry mouth and thirst but not fruity breath. Each of these conditions lacks the metabolic changes that produce the ketones responsible for the fruity breath associated with hyperglycaemia.