Fridge odors often linger because the foods inside are constantly emitting and mixing their aromatic chemistry. While many of us were taught that an open box of baking soda would absorb or eliminate such smelly encounters, you may have since learned that one box simply doesn’t work well enough. The natural properties of baking soda are rather localized in their effectiveness, so to eliminate all the odors you would need surface exposure on multiple shelves.
Activated charcoal filtering is an alternative that is known to work much better. It is often used in modern refrigerators equipped with a deodorizing system. Of course, it eventually needs to be replaced and that can be expensive, but pet shop and aquarium stores may sell it at bulk prices. You might also consider a battery operated refrigerator air-filter equipped with a small fan. However, you need to be aware that some such products claim to emit ozone (O-3) gas to eliminate odors. They should be avoided as ozone is considered toxic.