The cheapest EV would be a BYD Surf, but unfortunately you cannot find used cars of these yet in Europe. Too new. Eying those for a while
Of course if you look at the used market, older models like Renault Zoe can also be found for cheap... But considering EV technology have been evolving fast, I wouldn't buy a model older than 5 years old.
I also wouldn't want anything that doesn't have a CCS2. All my small electronics are finally USB-C, I don't want to deal with obsolete plug types and adapters again.