what state an agency is the academy for? Sounds like he will be well prepared...Ive been to two different academies, one was 6 month residential, another 6 home get to go home at night....as well I did 2 years at a military academy...in all these scenarios, you gotta remember these people are NOT all athletes....there are tons of people who probably couldnt make a high school sports team back in the day who are soldiers and cops (not saying its a bad thing), but if your buddy has been training his butt off regularly, the most he probably needs to prepare for is dealing with the mental games, or being annoyed by how some people react to stress around him and the group dynamics of it all.
So anyways, sounds like he is training alot, and there will be people who come in who havent trained but still make it. Its all about not giving up Im sure he will do fine.
Depending on the academy he may or may not be able to take supplements during the day (or at night if its residential and they dont allow personal items). If he can, Id do meal replacements and protein shakes to make up for whatever cafetaria junk food they have (mine was bad, but Ive heard of academies where they actually hook them up with good grub). If its a go home at night academy and pack your own lunch, keep up the good nutrition.
DRINK TONS of water. Get a good carb/protein workout mix to drink before the training sessions (I prefer Endurathon), aminoval fast charge packs would be easy way to shoot down some BCAA's really quick without needing to pop pills, and Im always a big fan of anti oxidant formulas.
Tell him good luck, and let me know where he is going! He/you can PM me if you have further questions.