I got a bit desperate and did this to my Chanel all leather flap with a strong odor (icky sweet humidity-related smell gave me headaches). Whenever the weather was humid, the odor was worse. I had ozoned it, anti-bacterialized it, sent it out for cleaning, deep froze it, etc.
Have the bag completely clear of odor that is due to soiling and is completely dry.
I poured a giant box of Arm & Hammer baking soda into a large garbage bag. Then I then placed my *clean* *dry* bag into the baking soda and shook it gently. It coated the entire bag and I left it sealed in the garbage bag and then in a sealed plastic container. I would "turn and coat" the bag twice a day.
After 2-3 days, I took the whole thing outside on a clear day and shook the bag out and gave it a good brushing with a softshoe brush inside and out.
Only on leather (mine was leather on inside too), only on a dry day, on a dry and clean bag. I would NOT try this if it is at all humid, I have a feeling the baking soda will only cake and create wet spots on the bag.
I did this last summer. It has been super humid the last couple of weeks and the smell is minimal. On a scale of 1-10, ten being strongest odor, I would say 1.5 now, or just barely because I am so sensitive to smell. Before then, it was always up around 7-8, even after I had it professionally ionized.
I only recommend this if you are brave enough and desperate enough to try it like I was!