In his book titled Shanghan Zabing Lun (Treatise on Cold Pathogenic and Miscellaneous Diseases), Zhang Zhongjing, an ancient Chinese physician from the Eastern Han Dynasty (25-220), wrote to prevent and treat heat stroke, the right way is to drink some hot water and sweat, as it is good for boosting blood circulation.
When the weather is sizzling, people's tastes change and so they turn to foods and drinks which they believe can help relieve "inner heat" in the human body.