Any rehab worth its salt should, at minimum, provide a medically-based detox process and individual counseling. After that, many/most spend the bulk of whatever time is left advocating the addict/alcoholic attend a 12-step program upon release or uses the time to initiate them into some other behavior-modification program, of which there are quite a few.
Depending on where your friend lives, there are
atheist/agnostic/freethinker AA meetings and
secular 12-step recovery groups that offer the fellowship and support of AA without the heavy-handed Judeo-Christian content found in the typical AA/NA meeting.
It is also possible to, with an open mind, to find and maintain recovery in regular AA as a freethinker; I have been in recovery in AA for almost 25 years; in less than a month I will have 23 years clean and sober.