Care Package for Someone in Drug Rehab?

Someone close to me has recently entered rehab for drug addiction. The facility does not allow patients to make or take phone calls, but they do allow mail to be sent to patients. What would be appropriate items to send? Of course a a great card…maybe some magazines or puzzle books, but what else? I am very hesitant to send any foods/goodies as I’m sure he will not be feeling well at all experiencing withdrawal symptoms. Any suggestions would be greatly appreciated!