When people come to my house and wonder why we have a tall stack of these 1 quart containers, we show them! We stack them like blocks too! We make walls and castles for Ezra to knock over. (He's our youngest.) All my children have fun making the castles and walls with the cartons.
I also use my yogurt containers for drinks on the go! I mix up my protein drink in the blender and pour it into my 1 quart yogurt container and put the lid on, with a small hole cut in the top for my straw. It's kinda' my signature... I will reuse these containers until they are beyond use. With this recycled container, I don't mind if someone tosses it in the garbage. Which can happen when I am out and about. I have tried other containers, but they were too tall for my straw to reach the bottom and be able to drink out of it.
We have also had loads of fun with the yogurt cup lids! They are safe indoor flying disks! And easy for little children to make fly! I think we had about 20 lids that we were flying at each other one morning. We were laughing so hard, we got our morning exercise!
The smaller 6 oz and 8 oz yogurt cups can be used like those stacking cups and they are are free, once you eat your yogurt! If you want to reuse those smaller yogurt cups, some yogurt companies will send you the reusable plastic lids for free if you ask. Then I put my husband's daily yogurt into one of those cups for his lunch from the larger 1 quart container. I think I need to learn how to make yogurt! When we take yogurt in the car, I put a hole in the top and stick in a straw for less messy eating! It works most of the time. Some of those yogurts with bigger chunks of fruit might get stuck... I can even cut the straws in half for a more convenient size.