Hard-sided container or the backpack wall.

The trick is to give the sandwich its own rigid container, then pack it vertically against your back.

Soft lunch bags are the problem. They fold, and whatever is in your backpack folds with them. A hard plastic or metal sandwich box takes the pressure instead of the bread. That alone fixes 90% of crushed-sandwich commutes.

Pack the box upright, standing against the back panel of your backpack. That way your spine and the backpack frame take the hit, not the bread. Put heavier stuff like books or a laptop on the bottom, and keep the sandwich out from under them.

If you don’t want to buy a hard box, shove the sandwich between two flat objects, like a notebook and a folder, but that only works if those aren’t getting squished either. Honestly, a $5 container is worth it.

Future sandwiches deserve better than a sad, flattened existence.