Is there an English equivalent for "Les carottes sont cuites", while keeping the vegetable reference?
Solution 1:
Although this isn't about vegetables specifically, I'm going to add it anyway—just so it doesn't get lost if comments are removed:
His goose is cooked.
From Wiktionary's entry for goose is cooked:
(idiomatic) All hope is gone; there is no possibility of success; the period of good fortune is over.
If he doesn't win the next round, then his goose is cooked.
My personal experience with this idiom is that it can not only imply just bad fortune, but also terminal fortune.
Of course, a more generalized idiom, which doesn't carry quite the same specific weight—and which also doesn't mention vegetables explicitly (but could still imply them), is out of the frying pan into the fire:
[Wikipedia]
The phrase out of the frying pan into the fire is used to describe the situation of moving or getting from a bad or difficult situation to a worse one, often as the result of trying to escape from the bad or difficult one. It was the subject of a 15th-century fable that eventually entered the Aesopic canon.
Solution 2:
You could say, "Stick a fork in him, he's done" -- which is an analogy to baked potatoes that would be commonly understood to mean that the subject is dead or otherwise expired, in North America at least -- not sure if this expression is good on both sides of the Atlantic though.
Solution 3:
The phrase that comes to my mind is:
He's had his chips
From Farlex Dictionary of Idioms:
To be defeated; to fail completely; to die or be killed.
Now, being British, to me "chips" are what others may call "fries" (think of them as in "fish and chips"). A potato is technically a vegetable, even if it doesn’t count as one nutritionally. Chips come with a main meal, like (cooked) carrots.
Sadly, in this phrase "chips" actually refers to casino tokens, but never let pedantry get in the way of a good pun!
Solution 4:
There probably isn't anything quite like what you're looking for, unfortunately. A quick perusal of wikipedia's list of death expressions and death euphemisms, as well as a glace at some lists of vegetables to try and jog my memory doesn't yield much - maybe the closest is "brown bread" which while possibly vegetarian, is not quite on the mark and likely not terribly common/well known at any rate.
But honestly, I would strongly recommend that you make up one of your own.
English is a terribly silly language(as are most, in all likelihood), and if you're writing a short silly story, homemade euphemisms will probably go over exceptionally well (depending on execution, of course).
"No! Don't do it!"
There was no trace of the normally rich, velvety baritone - anguish tore through his voice like a grater shredding cheese.
"It's too late, Sergeant Spud. This tater's been mashed."
I am exceptionally sorry for that. Please accept the musical stylings of Kip Addotta as my apology.