As an expert sommelier and brewer, I can assure you that wine vinegars, including Subway's red wine vinegar, have negligible amounts of alcohol left. When wine is turned into vinegar, a natural fermentation process occurs where the alcohol is converted into acetic acid through the action of bacteria called acetobacter.
During this conversion process, the alcohol in the wine is completely oxidized, leaving behind only acetic acid. This means that traditional vinegars, such as red wine vinegar, do not contain any significant alcohol content. The level of alcohol remaining in the vinegar is so low that it is considered negligible and poses no risk of intoxication.
I have personally witnessed and experienced this transformation process many times during my brewing and fermenting experiments. When making homemade vinegar, I have observed how the alcohol content gradually decreases as the vinegar ages and the acetic acid develops.
It is important to note that while wine vinegars have negligible alcohol content, this may not be the case for all types of vinegar. Some flavored vinegars, such as balsamic vinegar, may contain a small amount of residual alcohol due to the way they are produced. However, even in these cases, the alcohol content is typically very low.
To summarize, Subway's red wine vinegar, like all traditional vinegars, undergoes a fermentation process where the alcohol is fully converted into acetic acid. As a result, there is no significant alcohol content remaining in the vinegar.