Little is currently known of this particular meme as much hasn't been made of it.
But this little joke made it's debut on the American Sitcom : Friends where Actor Matt LeBlanc plays character Joey Tribbiani, a (at times) hopeless being when it comes to love.
During an episode, Actress Jennifer Aniston (Rachel Green) is having quarrels upon how she would get a date, out of own will Joey gives her his advice, he simply puts on a 'Mobster' accent and says 'Hey, how YOU doin'?'.

Considering the show was aired in the 90s /00s, this 'joke' took a little while to make it to the internet.
But eventually, it did. The phrase made it's way onto pictures in captions, the phrase is normally found upon a picture of a male/female figure looking at someone/anything in a seductive manner. This joke can be used in both appropriate and inappropriate manners, because a meme wouldn't be a meme if it couldn't be used 'inappropriately'.

A few seconds of looking at google images with the criteria 'Hey, How YOU doin'?', you will understand what context it is used in.