I’ve started using little glass canning jars as lunch containers. You can get them quite cheap in the kitchen supplies section of a big Target store. They get cleaner than plastic containers when you wash them (no food odors hanging around!) and if you take the tops off, they’re microwave safe. Freezer safe too, according to the package, and dishwasher safe. (The tops might rust after too many times in the dishwasher, but can easily be replaced with any jar lid of the same size.)
Eight of them in a little lunchbox, filled with things like squash, lentil soup, watermelon chunks, mixed nuts, crackers, cottage cheese, yogurt and applesauce, is enough to get me through a full day at work.
Also, if you can find this pumpkin-spice cider at Aldi, it’s delicious, and the bottles make great, well-sealed water containers to take to lunch.