How to Fix Smelly Plastic Containers
If your plastic container has an unpleasant smell, you can get rid of it with a few household ingredients. One easy method is to use white vinegar and baking soda. First, mix 1 cup of white vinegar with ¼ cup of baking soda in a large bowl. Place your plastic container in the bowl and add water until the container is submerged. Soak it for 1-2 days, then wash it in the dishwasher or with soapy water to get rid of the smell of vinegar. Alternatively, place a large pinch of salt or used coffee grounds in your container, seal it, and leave it for a day to absorb the unpleasant smell.
Remove all food remains. If you are trying to get food smells out of the plastic container, make sure that you have removed all food scraps. If you are having trouble getting food remains off the inside, try to use an object like a spatula and scrape the food off, or run warm water onto the container and scrub off dried food. Wipe away grease or oil. Even if you have gotten rid of food scraps, you still may have a greasy residue on your container. Wipe the container thoroughly with a paper towel to absorb oil or grease. Soak the container in water and dish detergent. Soaking your container can ease out stubborn bad odors. Fill the sink or a large bowl with warm water, then pour in a generous amount of dish detergent. Let the container soak for at least thirty minutes. If just soaking the container didn't remove the smell, scrub the container with a scrub brush while it is still submerged in the water. This should work the soap into the container, so that it can pick up the offending odor. Dry the container. Take the container out of the soapy water. Give it a quick rinse to wash away soapy residue. Dry the container with a cloth or paper towel. Then sniff it to see if the odor has gone. If the bad smell is still there, sprinkle some baking soda over the container and let it sit for a few minutes. Then, wash it out again. Put the container in the dishwasher. Make sure that your plastic container is dishwasher safe, then stick it in the dishwasher and put it through a cycle. The high heat of the dishwasher may work to remove the odor if you have not been able to get it out through hand washing. Put the container on the top rack to prevent warping. Make a vinegar and baking soda mixture. If you didn't have any luck with just soap and water, you may need to use more powerful cleaning ingredients. Take a large bowl or pot, and pour in a cup of white vinegar. Then add ¼ cup of baking soda. Stir the baking soda into the vinegar until they are mixed. Add the plastic containers and some water. Drop the plastic containers into the bowl with the vinegar and baking soda, remembering to also add the lids. Then add enough water so that the containers are fully submerged. Stir the mixture in the bowl with a large spoon. Let the plastic container soak. Keep the plastic container in the mixture for 24-48 hours. This will allow the vinegar and the baking soda to thoroughly work to deodorize the container. Put the plastic container in the dishwasher. The baking soda and vinegar should have deodorized the container. However, vinegar can leave behind a strong scent itself. This is why you should put the container in the dishwasher directly after the container is done soaking in the mixture. If you don't have a dishwasher, scrub thoroughly using water and dishwashing detergent. Absorb the odor using salt. If washing and soaking the container don't work to absorb the odor, you can place absorbing agents inside the plastic container that will absorb bad smells. Salt is one such substance that can be used to absorb odors. Add a large pinch of salt to the inside of the container and leave it in a clump in the middle. Then cover it with the lid and leave it overnight. Just make sure to wipe out the salt before you use the container. Place crumpled newspaper in the container. Newspaper can also absorb bad odors left inside plastic containers. Take several sheets of newspaper, then tear and crumple them and place them inside the container with the lid on. The paper should soak up the bad odors if you leave it there for 24-48 hours. Wash the container after taking out the newspaper, since the newspaper may be dirty. Use coffee grounds. Coffee grounds are great at absorbing odors. After making the morning coffee, place the used coffee grounds in the plastic container. Used coffee grounds work better than fresh ones. Put the lid on and let the grounds sit in the container for about a day until the odor is gone. Put the container in the sun. Place the open plastic container outside on a sunny day. The sun has great odor-fighting abilities, and leaving the container open will allow the container to air out. If you aren't able to put the container directly outside, you can also just put it on a sunny windowsill. Use vanilla extract. Vanilla extract has a powerful, pleasant smell that can mask the bad odor of your plastic container. To use vanilla extract, put a few tablespoons of water in the container along with a few drops of extract, then shut the container. You can also pour the vanilla on a cloth, put the cloth in the container and close the lid, leaving the vanilla to permeate the container for several hours. 
Remove all food remains. Soak the container in water and dish detergent. Dry the container. Put the container in the dishwasher. Make a vinegar and baking soda mixture. Add the plastic containers and some water. Let the plastic container soak. Put the plastic container in the dishwasher. Absorb the odor using salt. Place crumpled newspaper in the container. Use coffee grounds. Put the container in the sun. Use vanilla extract. 