The lunch box it’s one of the best inventions, because you have the ability to eat healthy at work, school, everywhere, without spilling your food and keeping it in great conditions.
But these boxes have a small inconvenience: after a few uses they catch an unpleasant food odor even if you wash it. Also, grease is hard to remove from that plastic material they are made of.
If are know well this situation then you have to try the next cleaning your lunch box methods instead of throwing it. I heard that some of my co-workers do that, but I prefer washing it and eat my lunch from my favorite box.

In the weekends, when you don’t use the lunch box, or right after work, just sprinkle coarse salt in it, but after you have wash it completely with dish detergent. Then, put the lid on and wash it again in the morning.
If you use this remedy in weekends, repeat the procedure 2 days in a row.

The Sun
Strong sunlight can eliminate the unpleasant odor from your lunch box. All you have to do is wash them well with warm water, and then rinse them with cold water and let them stand open in the sun. Either put them on the balcony or on the window sill. Keep it there for a few hours or as long as the sun is still up.

Vinegar is the best ingredient when it comes in removing odors. It probably sounds strange considering that vinegar has a strong and persistent odor. Just wash the lunch box with water and detergent, and after rinsing it well, pour vinegar in it, put the lid on and star shaking well the lunch box. Let the vinegar stand for 5 minutes, and then rinse it again. Leave it to dry.