Congratulations on 4 months of sobriety!
Although abstinence is key to success for all of us who are alcoholic or identify as a problem drinker, I think there may be some variations in how we approach it. For me that means abstaining from willingly, knowingly or purposefully imbibing alcohol in the context of eating or drinking whether alone, socially or recreationally. For me upfront abstinence and stopping if becoming aware of a breach.
For me other forms of alcohol have never been a temptation or held any appeal to abuse, so to be honest I've never even given any thought to mouthwash. Oddly enough now that I think about it, I'd probably steer clear of cold / flu preparations such as Nyquil where I would go through the motions of pouring a cup and drinking it.