Plastic wrap.
Plastic wrap has the advantage of being transparent, so you don’t have to open it to find out what’s inside. Plastic wrap is good for making an air-tight seal on bowls or containers that don’t have a lid. However, plastic wrap typically can’t be re-used.
When it comes to the microwave, the plastic wrap should be at least one inch from the food that’s being heated. The heat from the food could cause the plastic wrap to melt
By the way, users of foil and plastic wraps may not have noticed that the boxes often have a handy tab at the end that you can press to keep the roll in place. (I had no idea, either, until I read about it on TipNut.)