Hello, new to this forum and read through your thread, I spent two years in Iraq and 1 year in Afghanistan, and know a few items that could be of help.
1) Beef Jerky - This stuff is awesome over seas and really hard to get, a few of the big bags will last for weeks
2) Ravioli Cans - This stuff is awesome also, sometimes that chow hall really sucks, and its good to have a good ol' can of Ravioli or Spaghetti and Meatballs
3) Water Heater with Ramen - If your friend likes ramen, buy him a small water heater, it usually costs about $10-$15. This can be plugged into a HMWV or into an UPS, and it heats the water in 2 min. This is also useful for shaving, coffee, tea, etc.

4) Baby Wipes - Baby Wipes are like gold, we use them for everything, cleaning our weapons, cleaning our gear, cleaning ourselves, used in the wash room, everything.
5) Q-Tips - Just like the baby wipes, we use them for everything, weapons, ourselves, and helps get the dirt out of smaller equipment
6) Hand Sanitizer - The Chow Hall usually offers this but is good to have on the road, usually uses it during chow time or after cleaning gear
7) Kool-Aid Canisters - I loved these while I was over there, we are given huge bottles of water and Kool-Aid makes it better. The huge tubs last a long time, I would send two or three different flavors
8) Candy - Stuff like suckers, life-savers, gum, etc are really good, things that won't melt and can be carried around in a pocket or small bad.
9) Condiments - The chow rarely has good condiments, so I would send small bottles of Tabasco (if they like it) salt, pepper, season salt, garlic salt, etc. I would always carry something to the chow hall to put on my meal, and they work well in MREs too.
10) Books - nothing beats the work day like a good book, I read a ton while I was over there. My parents sent me an E-reader with a ton of books on it, never put it down.
11) If he has an ipod or computer, send him some music or movies, these are great for down time and increases moral.
12) Stuff for letters and packages.
There are a lot more things, it just depends where he is at and what FOB he is on. If you have any questions please ask.