Cash, grocery card, something like that that is practical and useful.
I don't know what his situation is, but I struggle pretty hard to make ends meet. If he's like a lot of guys (and since he didn't want to tell anyone waht was going on, I'm guessing he is), he may be hurting in a lot of ways, including financially, and will keep it to himself.
He's probably dealing with a lot of emotional stuff in the aftermath, especially if his ex wife did such a radical change in her lifestyle. Letting him know you guys are there to support him will mean a lot.