Using your knife, thinly slice lemons and place them at the bottom of the container. Cover the container with the lid (most likely also very smelly) and place them in direct sunlight for as many hours as you can. The two work together to remove smells.
If this does not work, move to the next Step.
Baking soda can be a valuable friend in times like these. Pour some of it into the container and slowly add water. Mix the two together until they form a paste. Using the toothbrush, rub the paste into and around the entire container, including the lid. Allow the container to sit for 30 minutes to 2 hours depending on the severity of the smell. Rinse the container with warm water.
If possible, allow the container to air dry in direct sunlight as the UV rays will aid in removing the smell.
The last suggestion from us is to pour distilled white vinegar into the container. Allow this to sit for a few hours. Vinegar acts to remove smells, however, the bad smell will be replaced with the smell of vinegar, which is most likely more pleasant and much easier to get rid of with some thorough washing.
Wash and rinse the container vigorously. Once again if you are able to allow the container to dry in direct sunlight it will go a long way.