If you are talking about the plastic tubs, I used those to hold the dirty litter after scooping. With the plastic lid, it held in the smell until it was full. When I emptied the entire pan, I'd pour it into the plastic tub.
If you are talking about paper type containers, I just use those as garbage bags.
I have a bunch of plastic buckets from years ago when I'd buy their food in buckets. I use those to hold craft items, painted some and used those to hold kindling by the fireplace, store chemicals in the garage that I don't want critters to get into, and use one as a compost bucket under the sink. When you live in the country, you NEVER throw away a plastic bucket!