Source for vinegary smell on leak?
The pipe with the corrosion is a SUPPLY pipe, not a drain pipe, so anything having to do with pouring vinegar down a drain would be irrelevant.
That coupling looks bad, as in someone did a poor job of soldering it, maybe used the wrong flux and there is a pinhole leak. The white material looks like a calcium deposit, likely from that pinhole leak and the water evaporating, leaving behind that calcium deposit (think stalactite in a cave). The blue material is copper oxide, a residue from corroding copper.
My guess given that evidence: the previous homeowner did his own copper plumbing (or hired a cheap handyman to do it) and made a mistake on that fitting (which would make me worry about others) right before putting the house on the market. Rather than re-do it, he may have just tried to clean off the calcium deposit. One way to do that is to use vinegar! But then the vinegar also reacted with some of the exposed copper and formed the copper oxide too.
Bottom line, I would not get too into the vinegar smell issue, you have a bad coupling that needs to be removed, the pipes cleaned thoroughly and a new one soldered in properly. If you don't have the skill set for this yourself, hire a plumber.