I always use M9 in my bag and one of the ostomy odor eliminator sprays. Spray the air before you empty. Gentell Ease Odor Eliminator. I also change my bag every other day because the longer I wear it, the smells become stronger in and around the bag, and nothing reduces the smell. The Gentell Ease Odor Eliminator is cheap, about $3.00 for a 2 oz bottle from an internet ostomy shop. Do not buy from Amazon; it is nearly $8.00 a bottle.
Cheap and it does the job!