Do you put in black tank treatment pod prior to storage?

If it makes you feel good, go for it...but it doesn't do anything.

There are plenty of bacteria and enzymes already present. As long as the solids don't dry out, they will break down just as fast with no additives.

A little water so solids don't turn to cement on the bottom isn't a bad idea but if you drained and flushed, that isn't even needed.

If you have odor issues, most likely problem is a blocked vent. Fix the problem, don't just add perfume to cover it up.