Some people feel fine with diluted vinegar water, but it is not universally “good for the stomach.” Because vinegar is acidic, it can worsen reflux, gastritis, ulcers, or general stomach sensitivity. If you notice burning, pain, nausea, or increased belching, vinegar water is not a good fit. If you tolerate it well, a low, diluted amount may be acceptable. The key variables are dose and dilution. If you already have stomach issues, be conservative or avoid making it a daily habit.