Well, I often did this when I was younger and still living at home. Since I was forbidden to drink from the juice/milk container directly, I would circumvent my mother's warning about putting my lips on any communal container by pouring it into my mouth without letting my lips touch it.
That way, when my mom would holler from another room that (I swear she could hear the refrigerator opening from across the house) I had better not be drinking out of the milk jug, I could yell back that I wasn't, which was technically true. Of course her intent was for me to pour it into a glass and drink from that, but I felt it was a fair compromise. She didn't quite view it that way. :lol:
Of course once I started living by myself I was then free to drink directly from the container since I was the only one using it.
I still make a point of drinking directly from the container in front of my coworkers for anything I keep in the office fridge. Single serving bottles and cans tend to disappear, but nobody touches my half-drunk gallon of juice/tea when they've seen me drinking directly from it. It also eliminates requests to share.
It does seem like one of those things we need a word for. I'll sometimes still do it when I need to drink from something like a water bottle but don't want my lips to touch it.