It's generally best to store sapota and bananas separately. Bananas release ethylene gas, which can accelerate the ripening and spoilage of sapota.
Bananas are known as climacteric fruits, meaning they continue to ripen after being harvested. This ripening process involves the production of ethylene gas. Ethylene acts as a ripening hormone, affecting not only the banana itself but also other fruits nearby. Sapota, while also a climacteric fruit, is more sensitive to ethylene. Exposure to high concentrations of ethylene, such as those emitted by ripening bananas, can cause sapota to ripen too quickly, leading to a shorter shelf life and potential spoilage before you have a chance to enjoy it. Storing them separately helps control the ripening process and extends the freshness of both fruits. If you want to speed up the ripening of a sapota, then placing it near a banana for a short period can be helpful.
If you must store them together, keep the bananas in a perforated plastic bag. This will help to contain some of the ethylene gas while still allowing for air circulation, slowing down the ripening effect on the sapota.