30 Day by day the king gave Jehoiachin a regular allowance as long as he lived.

Read 2 Kings 25:30 Using Other Translations

And his allowance was a continual allowance given him of the king, a daily rate for every day, all the days of his life.
and for his allowance, a regular allowance was given him by the king, according to his daily needs, as long as he lived.
So the king gave him a regular food allowance as long as he lived.