Mouthwash, (also termed mouth rinse) an antiseptic solution will kill oral bacteria. Certain bacterias are needed to process nitric oxide which helps prevent metabolic syndrome inc. Diabetes. Yes bacteria can cause bad breath but we live in a balance with bacteria on and in our body.
Study (3 years) in San Juan showed individuals that used mouthwash twice or more a day had an increased risk (55%) of pre-Diabetes or Type 2 diabetes vs. those that did not.
Mouthwash does not replace brushing teeth nor flossing them, actually there is no real reason according to American Dental Association to rinse.
Perhaps worth considering?