Ever drink water first thing in the morning and feel instantly nauseous? That’s your stomach lining being a drama queen. When your stomach is empty, the water can dilute the natural acids and digestive juices just enough to cause irritation or a "washing-machine" effect.
Can Sparkling Water Hurt Your Stomach at Christopher Larochelle blog
It’s like pouring water into a completely dry pan and then trying to fry an egg—the surface acts weird. A little bit of food or even a cracker before you chug can coat the lining and prevent that watery revolt.
