Sweating itself does not burn many calories. It is mainly the body’s way of cooling down when temperature rises, such as during exercise, hot weather, or being in a warm room. The calories used come mostly from the activity your body is doing, not from the sweat.
For example, a hard workout may make a person sweat and also burn calories, but the calorie burn is due to muscle movement and increased energy use. Sitting in a sauna or wearing extra layers may cause heavy sweating, but this mostly leads to fluid loss, not fat loss.
Any quick drop on the scale after sweating is usually water loss. This weight can return once fluids are replaced. Sweating more also does not always mean a better workout, since sweat levels vary from person to person and depend on heat, humidity, fitness level, and clothing.
For healthy weight loss, regular physical activity and balanced eating are more reliable than trying to sweat more. Drink fluids as needed, especially during exercise or hot weather. A doctor or registered dietitian can help create a safe weight loss plan.