Hi Lessara,
Hello, how are u?
How about cans of tuna, sardines in olive oil (get those ones with the pull-tabs) & packets of mayo.
Do u have a fridge at work? Maybe u can put a couple of cooked meals (in microwavable containers) in the freezer compartment. So if u forget to bring lunch, u can have them as an "emergency meal".
Have a great day

Bebe