How to not enable?

How can I keep my Q in my life without enabling their addiction? I’m referring to a very close friend of mine who’s drinking has become part of every activity we do. I’ve asked him to not drink when we do daytime activities like hiking, but he always seems to sneak some form of alcohol along.

He doesn’t have a car so I usually drive, and recently he started cracking open a bottle in the front seat out of nowhere while I was driving and I put my foot down.

I tried setting a boundary of asking him not to drink in certain settings (hiking trail, car, etc) but he just ignores it. I don’t want to cut him out of my life completely because his support system is not good and I want to help him get sober, but I’m afraid if things continue as is I am just enabling him.