Mouthwash is actually not only ineffective, it is directly linked to increased blood pressure and hypertension via reducing bacteria involved in nitric oxide production which influences blood pressure.

“Conclusion: In this study, frequent regular use of over-the-counter mouthwash was associated with increased risk of hypertension, independent of major risk factors for hypertension and several other potential confounders.”

Another:

“Critically reviews evidence from a published study that suggested mouthwash use is associated with increased risk for prediabetes/diabetes.”

“those using mouthwash twice daily or more at baseline had an approximately 50% increased risk of developing prediabetes/diabetes combined, compared to those who used mouthwash less than twice daily or not at all.”