"Granted, they were obsolete; the subs were of the diesel electric variety, not nuclear ones" - That has not stopped countries in the past from selling ships, tanks, trebuchets, or anything else that can generate revenue.
The USSR at this time were cash strapped and finding a way to clear out some inventory while getting cash in return likely was seen as an easy win.
That being said I wonder if Pepsi had kept them if they would have named them after their other drinks? we could of had the Pepsi Fleet Ship (PFS), Mountain Dew? Or the PFS 7-UP Heavy cruiser?
Regardless thanks for sharing the interesing article @warheart1992