It's a virtual certainty, as in It's dollars to doughnuts that the team will make the playoffs. This metaphoric term pits dollars against doughnuts as in a bet. [Colloquial; late 1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.