My husband take his lunch to work several days a week. Usually what he takes is just dinner leftovers. This is super easy because I just pack it up as we are putting away the leftovers from dinner. And I always make extra dinner, so that we have plenty of leftovers.

My kids lunches are always things that can be eaten cold or at room temperature, because they don't have any way to heat things up. But my husband works in an office, with easy access to a kitchen with a microwave. So a hot meal is a nice option for him. And sending him with leftovers means that I don't have to make something separate.

We went through a lot of different containers before we found one that works best for him. After a lot of trial and error, we settled on these microwavable containers from Sistema. We like them for several reasons:

They are made for the microwave - they have a vent at the top that you just pop open.
They do not leak! He carries this sideways in his computer bag and has never had a leak!
They are relatively flat - as I mentioned, he likes to just slip this in his bag, so he wanted something that wasn't going to take up a lot of space and these work just great.
They come in three sizes, so you can pick the size that works best for your size meal.

We use the medium size most often, it seems to be just right for lunch. But the large is also nice for when you want a bigger meal. I actually don't have a small one, since I got these for a man sized appetite, but it looks like a nice size for a smaller appetite.

Honestly, I don't love the color. I don't think food looks very appealing on red, but whatever, they work so great that we don't worry about the color.