[KimMG]

Make sure the drain for the fresh air intake for the heater and A/C is clean and clear of leaves, debri, standing water. There should be a small drain tube.

Other than using Lysol or something similar, the only thing I can think of is to take the system apart and cleaning the parts in the dishwasher. This would be really involved.

If you have doubts about the existence of a cabin air filter, the best person to ask at the dealership would be the person at the parts counter.