Gotta start drinking again, the reason your hungover A) dehydration so do drink water B) that alcohol has left the system so get some back in just take it easier
Hangover results from electrolyte imbalance and dehydration. Even though the best way to prevent is to "treat" it before you go to sleep...i.e. drink water and hydrate, you can still obviously fix it the morning of. What works for me is coconut water. 1-2 glasses and i am back to 100%.
https://www.morningrecoverydrink.com/ Works, but you have to remember to drink it before you sleep. You also still have to hydrate. In the morning, coconut water is always awesome.
One time I had hangover for 1 week. I was paralyzed in my bed with vertigo. I think that was alcohol poisoning
Sleep Aleve Cold shower Starbucks iced coffee - venti Fresh air for a short while Pho or another soup
In addition to dehydration, your kidneys also need a load of water to flush all the nasty alcohol metabolites, so fluids are doubly important. Honestly, an IV and a bag of lactated ringers is your best bet. I hear that there is some place that sells IV's for hangovers around town. I think they put vitamins in it too, or something. Otherwise force so much water down your throat that you have to pee every 15 minutes. It'll probably make you a bit sick to your stomach at first, but it will pay off fairly quickly. As far as painkillers for the unpleasantness in the meantime, acetaminophen and alcohol are toxic to your liver. No Tylenol. Try your favorite of the other three OTC painkillers.
While he's at it I guess he can stop trimming his bush. My EMS buddies would give the entire firehouse IV's first thing when they came on shift. There was also a "Z-pack"? or something like that? I personally like the Starbuck's Doubleshot. And a quart of water. And a bit of food.