At the very minimum, this type of mail would incur the $0.46 non-machinable surcharge because it’s smaller than one of the minimum USPS dimensions for postcards, namely that one size has to be 5 inches (127 mm exact). You may also have issues with it being too floppy for basic handling by the postal carrier, especially if it was previously left in a warm mailbox.

But perhaps a more practical issue may arise first: will stamps even adhere to the wrapping of a Kraft Cheese single? If you cannot affix postage, that’s the most immediate impediment.