Find a large basin and put half a basin of water, put the food or sushi in a crisper, put it in the basin, and cover it with a small basin to prevent the water from leaking out.

You can see water on the outside. It is to seal things with water. It can be stored for 2-3 days if it is isolated from the air, so it should be fine.

It was like this before there was no refrigerator