Bad breath!!

*Please note: not asking for health advice. I have just found that GP's tend to refer to specialists and we don't have the money to go from one specialist to another finding answers so I'm looking to narrow our search with any experiences others have had.**

Hi all
Wondering if anyone has experienced bad breath and found the cause.

Hubby has bad breath. It has come and gone the entire time (14yrs) we've been together (and very likely before that). It can smell out a whole room when he's in it.
He's seen a GP about it previously and they just said halitosis and prescribed Somac, then kicked him out. But Somac doesn't stop it and only helps a little. Nothing I've found online helps it. Breath mints don't help.

Recently my 3yr old has started waking up with it too!

When they get it, it's lasts for a few days/weeks and then goes away on its own. Both start snoring when they get it.
It might be a gut health thing but my daughter has allergies so hubby and her have different diets. Both take probiotics.

Both have seen dentist and they have ruled out dental reason for it. Both have good oral hygiene.

Both hubby and daughter have had their tonsils removed. I'm wondering if it might be an ear nose throat thing? Or an infection of something that normally tonsils would catch?

Has anyone experienced this before? What was the cause? What helped or got rid of it?

Thanks all