Do I trust him?

I have been seeing my bf now for a month, he is a recovering alcoholic and has had many years of battling with his addiction, I have known him throughout this time. He has said this time he is going to stop drinking for good as he wants to have a life with me, have kids, get married etc .. He has been going to lifeline on and off and has said he is going into rehab after this new year. Today have had concerns that he is drinking again, he always carried this bottle around with him saying he has been told off the doctor to do it as he needs to keep hydrated .. But when I sniffed the contents it smelt like cider which is what he used to drink as an alcoholic. He says he is not drinking but can I trust him??? Please help!!