sulphate reduing bacteria can feed on choline, sulphur (including methionine from meat), hydrogen (from other bacteria) etc and depending on what they eat you have different smell.

Take vitamins/minerals. Lots ‘C’. Avoid soda, refined sugars and junk food.

You don't get the intollerance thing.

You write:
"I don't really eat that many products that have soy lecithin. However, I still smell bad to people."

You do not have to eat "many products" to react on something you are unable to tolerate.
All you need to eat is just one single product.

For example,
95% of store sold bread contains soy lecithin as emulgator.

Over 95% of cakes, cookies, deserts, chocolates (just about anything made with flour, chocolate, and fat ) sold in an avreage grocery store or a restaurant contains soy lecithin.


If you just eat some bread, or just one cake , that is enaough, you are going to smell!


Make your foods from scratch, and you will know hat you can tolerate.
If you eat at a restaurant, you ill never know for sure what you are eating.

WS

you don't know what you are talking about