Yes Ethan. he pours whiskey in Ennis' mug - and you can even hear Ennis thanking him (ok, it was just another Ledger mumble but it is actually a thank you).
I noticed that as being a bit of a weird scene. When Ennis comes back to the camp after his encounter with the bear, he drinks from the bottle. The fact they don't share the bottle is interesting as their level of intimacy is still evolving. You can also notice that Jack opens the bottle with one hand only.
I also like the way he moves his boot far and near to the fire trying to find a right place to warm hi feet without burning - very nice detal.