Coupons can be used overseas for up to 6 months after expiration! If you are interested in donating your expired coupons to the military here is the group that I follow on Facebook.
There are stateside locations you can mail to (that will distribute to bases around the world) as well as an "adoption" site where you can adopt a family overseas to send your expired coupons to. If you don't want to adopt you can also mail your coupons directly to a military base listed and the coupons will be distributed.
(the group did not ask me to endorse them here, I just wanted to get their name out there if anyone was interested in donating!)