Edited to change this to a link to fanfiction.net:http://www.fanfiction.net/s/7519286/1/The_Hostess_Bar
It's the grand re-opening of Madame Christmas' hostess bar, and Mustang brings his whole team -- including a very unhappy Hawkeye. Royai.
Spoilers for Episode 48 (Brotherhood anime) and Chapter 87 (manga) to end of series. Inspiration from Chapter 62 of the manga.