How long is your commute? I usually don't eat before I ride in, but by the time I get to work I'm hungry so I eat a banana, shower, and then have a muffin/scone or something similar at my desk.

I bring my lunch with me in a regular insulated lunch bag. It fits in my backpack or panniers. If you put the food in a hard plastic container (there are some big enough to hold a sandwich) it won't get crushed.