The cutie mark crusaders want to be grown-up mares like Applebloom's big sister, Applejack.
So when Applebloom finds out that Applejack has a secret cider stash, and Applejack tells her it's "For adults only" the crusaders decide that if they drink it, they'll be adults too. What could possibly go wrong?

This is an idea I had while drunk. Also I wrote it while drunk. Maybe I spend too much time drunk.