Because the morning is usually on an empty stomach, drinking at this time is drinking on an empty stomach. Drinking on an empty stomach, without food relief in the stomach, will directly stimulate and erode the gastric mucosa and muscularis, destroy gastric acid, inhibit the secretion of various digestive enzymes in the gastrointestinal tract, slow down gastrointestinal peristalsis, and easily cause nausea and vomiting, abdominal pain and bloating, loss of appetite, indigestion and constipation. My very best wishes to your health