Denmark gave Iceland Akvavit at a "country party" one time.
Here's how the night played out:

Iceland ran into a mirror to see if it was a "mirror that will take him to a magical universe"

He sang the AOT theme song

Then cried over Levi's friend's deaths

Then claimed Sweden was a colossal Titan and tried to kill him with an unsharpened pencil

Then asked him if he was Swedone with Denmark's shit

Then told Norway he was "hotter than that big yellow thing in the sky"

Then danced on the rooftop of the neighbor's house

Then jumped off that roof

Then called Denmark a pineapple and said SpongeBob lives in his head (something he doesn't regret)

Then attempted to smash a lamp on Canada's head.

Then sang Spooky Scary Skeletons before passing out into a bowl of fruit punch

Basic moral: Don't give Iceland alcohol.

*cough* Alfred got it on camera *HACK*