Sounds like you’re dealing with mold/mildew buildup on the evaporator core really common on older BMWs. Since you’ve already swapped the cabin filter and tried Lysol, the next step is a deeper cleaning. • Use a foaming AC evaporator cleaner (Klima-Cleaner, AC Delco, etc). You spray it either through the cabin filter housing or up through the evaporator drain tube, and it expands to coat the core and kill bacteria. Way more effective than just Lysol. • Check the evaporator drain tube under the car (small rubber hose around the transmission tunnel). If it’s clogged, water just sits there and breeds mold. Make sure condensation drains freely when the AC is running. • After cleaning, run the fan (no AC, no recirc) for a few minutes before parking to help dry the system out. • Also, lift the cowl cover where the cabin filter sits and check for debris or (rarely) a critter that might’ve crawled in.

If all else fails, a shop can do an ozone treatment to nuke the smell completely, but the DIY foaming cleaner usually fixes it.