The short answer: it's a mixed bag. Coffee can ease grogginess and a dull headache by boosting alertness and narrowing dilated blood vessels — but it's also a diuretic and can irritate your stomach and spike anxiety, so it's not a cure.
The upside
Caffeine improves alertness and can take the edge off a hangover headache. If a cup helps you feel human, a small one is fine.
The downside
Coffee is mildly dehydrating, and you're already low on fluids. It can also aggravate an irritated stomach and amplify the jittery dread of hangxiety.
The verdict
Have a small cup with a glass of water alongside — but don't lean on it as a fix. What actually works on a hangover.
The better move is prevention
Hydrate, pace, and pre-load with a Gush before you drink. The prevention guide.
Always drink responsibly. This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.