You can make a tray with holes slightly bigger than a pretzel piece and shake everything through the holes. What stays is everything bigger than the pretzel but all the pretzels and smaller go to a lower tray.

Then in the lower tray you have holes slightly smaller then the pretzel and you shake everything through.

Then everything smaller than the pretzel is on the bottom tray, combine that with the top tray and you’ve got yourself a prezelless snack mix.