Hi, Sweetie,
Sadly, the teeny tiny bit of warmth, or influence, you have over your bro is not what he needs to get well. You simply cannot inject a syringe of hope; it doesn't work that way.
What can you say?
You can tell him you love him, and that you wish him well. You can tell him that when (not if) he decides to get on the road to recovery, you will be there for him, cheering him on, supporting him in his efforts, and loving him. In the meantime, as far as I'm concerned, he is dead to you. He is not a living being in this state. Trying to have a relationship with someone so immersed in his addiction, is a study in frustration and heartache.
Peace to you...