Generally overnight water is drinkable, but try to finish drinking it the next day to avoid overnighting it again. In addition, there are requirements for the preservation of overnight water, if it is placed in cups, kettles and other containers without lids or limescale, as well as dusty, stuffy environments, it is not recommended that patients drink overnight to avoid bacterial growth causing abdominal pain, diarrhea and other adverse symptoms. Bacteria are basically inactivated in pure water or boiled pure water, and a short overnight stay does not cause bacterial growth, so you can drink it. But a long time overnight, and not sealed and preserved, the opportunity and place for bacterial growth and reproduction, then continue to drink overnight water or repeatedly boiled water, may affect the gastrointestinal function, resulting in abdominal pain, diarrhea and other symptoms. However, overnight flower tea, green tea, wolfberry water, barley water and sugary drinks are not recommended to drink after a long time, mainly because it is easy to breed bacteria, may also contain nitrite, often drink a lot of nitrite poisoning risk, may appear dizziness, weakness, rapid heartbeat, breathing difficulties, vomiting, and even coma, convulsions and other serious reactions, affecting physical health.