Question: what to do when you have bad hangover?
Answer: Hydrate. Consuming alcohol causes dehydration by increasing urination. ... 
Sugar boost. Alcohol causes low blood sugar. ... 
Coffee. Alcohol causes the blood vessels to dilate, which can cause headaches. ... 
Multi-vitamin. ... 
Go to bed with an empty stomach. ... 
Potassium. ... 
Stop drinking. ... 
Acetaminophen or ibuprofen.