Nothing really haha I've done it before. But, it doesn't taste very good, and you don't really get energized.
What Happens If You Drink An Expired Energy Drink?
Its not cool I once found a monster energy drink in my grandmas fridge and she said I could have it but I never asked her how long it was in there and I ended up drinking the whole can and I happened to see the experation date and it ended up expiring in like 06....yea its 2011 now and on my way home from her house like 45 min after I drank it I got a really bad headache and not even 5 min later a was on the side of the road pucking my brains out and it had to have been the monster cause it was the only thing I had that day
Maybe it was because you only had a monster that day.