I use hot water + bleach + washing powder. Make a mixture in a spray bottle; about 1 table spoon of bleach and washing powder each in 500ml water. Spray the trim thoroughly, let it sit for a minute. Scrub with a soft brush and clean with a towel.
Adjust the washing powder/bleach ratios according to your requirement.
For an added touch, you can steam clean the fabric. Use steam iron at max steam; minimum distance from the fabric surface, without touching it. It gives fabric a very nice plush feel, and takes away any remaining bad smell or bacteria.
I've done many cars over the years, this is what it does for me:

