The drive-thru, which apparently looks like a giant cereal box of Cinnamon Toast Crunch and a carton of milk will be giving out bowls of Cinnamon Toast Crunch in exchange for completing a "crazy challenge."
You can find the Cinnamon Toast Crunch drive-thru across from We Cook Pizza and Pasta restaurant near the South Rim entrance of Grand Canyon National Park. It'll be there today, Friday, June 23, 2017 from 10 AM to 6 PM MST and Saturday, June 24, 2017, from 9 AM to 5 PM MST.
Photo via Cinnamon Toast Crunch.