I disagree. If the sandwich cannot be sold because it’s expired, than it is no longer a retail item and the store can’t make money from it. The trash is fair game. Should be cleared first with the manager, however.
The government/courts have already ruled on this. They can take your mail and other items from your trash and use it as evidence since they deem it as public once you discard it.
I assume a sandwich follows the same guidelines.