Awesome socks would be thorlos, fox river, smart wool.
Anti-diarrea pills would be good.
Look at wal-mart for one of those spice shakers that have like 6 types of spices in it. I loved mine.
Canned meats to give him a change from the normal food.
I don't know if I would go with salt to compensate for the salt loss. I have heard both good and bad things about using it. I never used it when i was there and there was some times where I only had 1.5 liters of water for a day (and there was times I went 2 days with 1.5 liters of water). Check into stuff called gluconade I think thats the way it is spelled. REI carries it and maybe someone here has used it.
Some bungee cords would be good and tell him to keep his poncho somewhere close to rig up a field expident hooch. Helps to get out of the sun some.
Water purification tablets as a means of backup.

Things are getting better over there as far as living conditions. If you weren't getting shot at life would be livable (hate to be there but livable). My experiences over in Iraq are not the same as my buddy who just got back and his will not be the same as the next group to go over.