dollars to doughnuts, it's

be dollars to doughnuts that (something happens)

To be assured or certain to happen. (The idea is that one is so confident in a particular outcome that they would bet money against something less valuable). It's dollars to donuts that Kevin will be late tonight—he's never on time.
See also: dollar, doughnut, that

dollars to doughnuts, it's

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]
See also: dollar