I just love those sandwich boxes. Not the ones with the separate lid, but those one piece sandwich boxes. I have a bunch of older ones with Pokemon on them. Those things are great. They work great for portioning out leftovers and such. I never have to search for a lid.
They look like this..
Another favorite is the Crystal Wave soup mugs. DH will take soup, chili or leftovers in those things. They don't leak. He packs them in his lunchbox (he's in construction, so he needs a smaller cooler in case he leaves the jobsite). Then you pop the little seal on top, microwave your food and it's great. The handle makes it nice so you don't have to handle a hot bowl.
Those soup mugs also work great for Easy Mac. We eat regular oatmeal. I don't buy the overpriced instant kind. Those soup mugs work great for making a single serving of oatmeal. I put the quick oats, a little sugar and cinnamon. Then my son can add 1 cup of water, microwave for just under 2 minutes and it's done.
The mugs look like this..
A while back we bought 2 of the surprise packs. We got a ton of Pokemon stuff. My son was so happy since we've liked Pokemon for years. We got a cereral holder, snack cups, soup mugs, etc. You didn't have to order a minimum in order to get the mystery boxes. That was cool.
Tupperware is nice, but at full price it's expensive.
ETA.. those flatout bowls are neat. We took them with us to WDW last October when we did
free dining. If someone couldn't finish their counter service dessert (like a rice krispie treat or something) we'd put it in the flat out. It stored flat in DH's backpack. Then you expand it when you want to put something in it. It saved having a few treats from being squished.