title_body: Can I pour cans into a keg?
upvoted_answer: I have done this with homebrew beer, but never commercially-bottled beer. The issues should be the same, though:
  
  
  You will significantly shorten the beer's lifespan due to the oxygenation, but if you fill the keg as full as you can so there's little to no airspace at the top and you're drinking it all that day, you'll be fine.
  When you force-carbonate after sealing the keg, I'd recommend 10-15 psi of pressure.
  I have no experience with ciders, so I'll defer to someone else on that, although I can't see why it would be any different.