We have a jet tub that is used fairly infrequently, that is emitting a bad odour.
I keep the tub clean, and just did a "bleach" clean of the jets, etc. but the smell is still present.
Thank you for your help!

Some bacteria are hard to get rid of. I use a tub of water and a swimming pool chlorine tab. Let it run for 15-20 minutes and soak overnight. Drain spa and flush. Be careful with tab, it is a strong oxidizer.

There be an issue with bacteria and germs they are hard to remove. In my opinion, please do use chlorine tablets or bromine tablets. They might be helpful, but please do consult with an expert with the amount or quantity of oxidizer to be used.