Try rinsing or scraping the residue off to clean it. “Spatula-clean” is clean enough to recycle. Containers contaminated with food cannot be recycled. If you have a composting area, cardboard and paper with food residue can be composted instead. https://www.epa.gov/recycle/how-do-i-recycle-common-recyclables#:~:text=Try%20rinsing%20or%20scraping%20the,with%20food%20cannot%20be%20recycled)