A tablespoon of apple cider vinegar in a glass of water may increase that risk, but you don't brush teeth directly afterwards, but instead you eat something, wh

A tablespoon of apple cider vinegar in a glass of water may increase that risk, but you don't brush teeth directly afterwards, but instead you eat something, which will normalize pH. If you're in the habit of weakening the enamel and then immediately brushing your teeth before they can self-repair, that will be a problem.