Step 19 = De-germ the car inside, when you wash the outside.
Whenever you give your car a good wash on the outside, wipe down the steering wheel, indicator / wiper controls, gear stick, door handles, seat belt buttons and car key / fob with a damp (well wrung out) cloth with a dash of tea tree oil on it. Naissance Tea Tree Oil from Amazon (not the brand in the picture, which is good but pricier) comes in 100ml glass bottles (I buy it in a pack of 2 for £15) which are sent out in plastic-free delivery packaging - hurrah! Add an atomiser spray cap from Amazon (with an 18mm neck) to the tea tree bottle, for less-wasteful application (money saving in the long run). If you want to refill the small bottles, then 'Mystic Moments' on Amazon sells huge 500ml metal bottles of tea tree oil (admittedly with a plastic screw top) which will keep you going for a good long while. The large metal bottle is sent out packaged within a papery-card version of bubble wrap, yay!
If you regularly eat in your car and/or you have been in contact with ill people, then disinfect the car surfaces, mentioned above, more often.