I'm afraid my alcoholic brother is going to be worse when he gets out because I heard it's easy to get drugs. That really scares me.

Inmates can and do get most anything smuggled in. Drugs and liquor are available inside and outside, therefore you have to stop worrying because if you cannot get him to stay sober on the outside, he will be spending a lot more time inside. The user has to want to quit, your "wanting it for them" is just complicating your life.