I take the source and pretty print / run a beautifier on it, which mostly reverses the process.
Though the client not having the originals just makes me wonder what the original DEV thought they had to hide -- I would question the competence of the entire process and would start digging deeper to see how far the rot goes.
... and if there are other deep-rooted issued, that's when you tell the client they were hoodwinked and bamboozled, suggesting a rewrite from scratch.