I have been packing lunches for a loooooong time. My favorite all-time lunch containers are the two and three tier tiffins. They create separation and hold a whole lot of food, but their circular base form means they don’t fit too neatly inside a backpack. These days, the kiddo doesn’t want to carry an extra lunch bag, so we reconfigured her lunches into these IKEA 365+ containers. They are a decent size (about a quart) and the little dividers you can add on (a couple of bucks i think) can help create some separation between your sweets and savories or wet and dry stuff. I went with plastic so they would be less heavy, but there are glass and stainless steel options as well with universal lids that you can switch between them all!
Just putting it out there in case you are currently frustrated with those new lunchboxes or lunch systems that you started the year with. These were pretty inexpensive and even if they fall out of use for lunches they will be great for storing stuff in the pantry.