I've never had the chance... and I'm not sure what I'd do. I'm not grossed out by it, but at the same time, it isn't really a turn-on, either.
I saw a video, not all that long ago, of a pretty attractive woman in the bathroom with a female friend and a guy friend. It almost looked like they were out somewhere, and she needed to pump or was leaking a little. Anyway, the female friend was trying to help her express milk, and eventually, the friend sucked on her and spit milk out into the sink. The male friend wanted to try after that, too (I would have done the same!).
I thought it was funny that the female friend said that it tasted like honey nut cheerio milk
Edit- I just found the link to the video if you want to see it for yourself-
https://xhamster.com/videos/adult-br...ing-xd-xh2LFMz