Drinking Alcohol at High Altitudes is one of the main concerns most armature hikers have to deal with these days since all of them think that without alcohol there will be no fun in it. But to be frank its not always correct, you will find the most heavenly feelings during a trek to the mountains which alcohol can not gives you ever. Specially if you are in Himalaya, Alps, Andes, Rocky or even somewhere in Greenland, you will feel these moments multiple times a day. :).
One option is to celebrate you victory id to hold that precious moment until you climb down that damn mountain and celebrate it all at the end of the hike. Why i am saying all these is that since alcohol is a member of the benzodiazepine family and if you use as such drinks during a hike, it can suppress your breathing which results in low levels of oxygen in your blood. So you should therefore be avoided these type of liquids as a general rule. But on the other hand, if you feel great (I would say if you are a seasoned mountaineer only) a few beers at Namche Bazaar might not be a bad way to celebrate it at all ;-).
My personal experience is that drinking almost any alcohol above 15,000 ft is a bad idea and will leave you feeling much worse than you would expect.
Anyhow Coffee has no impact on acclimatization and if it typically takes several cups a day to maintain it. If you are a regular coffee drinker be aware that stopping abruptly could cause a severe headache that could be mistaken for a high altitude headache.