How do you give ammo to people on battlefield badcompany 2

If your talking about Multiplayer, then you can't. Sure would be nice if you could, but sadly it can't be done unless that person is carrying the same exact weapon you are and you die so that he can pick up your ammo. You can't give ammo in the campaign mode either, you can sometimes receive the ammo from your companions, but that is only under specific missions. Hope this helped! =)