small collapsible lunch bags found in many CVS, Kmart, Walmart etc.
reusable ziplock style sandwich bags
tinfoil
paper towel
the less you carry on a daily basis, the better, but food can be hard to stock up on at the office
one trick I used, was buying a cpl dunkin donuts wake-up wraps & throwing them in the freezer at work. they were easy to microwave as a mid morning or afternoon snack. was also lucky to be able to walk to Starbucks for snacks but they are expensive