The last chapter of Jeremiah is a recap of the destruction of Jerusalem and the beginning of the Babylonian Captivity. We've seen these events before, but we get to see them repeated over again: Zedekiah gets his eyes cut out after watching his sons killed. Yeah, cheery stuff.
But we also get to see the exiled King Jehoiachin let out of prison and permitted to eat at the table of the Babylonian King Evil-Merodach (and, yeah, you wish that was your name). So there's always a silver-lining and the book ends on this weird note of tentative hopefulness. Just as their former king is released from prison, so will the people as a whole eventually escape their exile.
In her book Jeremiah: Pain and Promise, Kathleen O'Connor comments that the ending of the book doesn't really have an ending—it just stops. She thinks that there are actually two other "endings." One is when Baruch writes down Jeremiah's prophecies, because this lets us know that even though J-Man won't be around forever, his words will live on. The second "real" ending is the prophecy of the eventual destruction of Babylon, which gives us some closure on the whole bloody business. (Source.)
After all the cataclysmic events in the story, the very last sentence ends with a pretty modest and anticlimactic detail: the formerly imprisoned King Jehoiachin is given "a regular allotment of food" for the rest of his life. On the other hand, the people who first read this text lived in a society where regular meals weren't always a sure thing. So having this basic need met was maybe a luxury worth mentioning.