A more polite but equally comprehensible version of "For fuck's sake". They'll know what you restrained yourself from saying. Can be used in both senses of the original phrase.
1. "Isn't that your girlfriend with Texas Pete over there Superted?"
"For fudge cake! I just bought the heifer a holiday!"
2. "For fudge cake, please refrain from sticking your fingers in the fudge cake."