Gastroenterologist Dr Shubham Vatsya has said tea, coffee or citrus drinks, banana or milk-based smoothies and raw salad are worst foods to have on empty stomach. "Caffeine...and acid directly stimulate...stomach lining...which can trigger acidity, burning, and nausea," he said. Smoothies can cause gas/bloating. Raw vegetables are high in insoluble fibre and on empty stomach, it can shock the gut.