There has long been a debate about whether to use milk or water in your hot chocolate. While it is completely subjective, many hot chocolate connoisseurs prefer it with milk.
Adding milk to your hot chocolate will give the drink a much creamier, silkier taste than warm water, which some say provides a disappointing and flat flavor.
Those who only drink watery hot chocolate because of dairy intolerance or dislike can opt for hazelnut, cashew, oat, or almond milk instead of cow's milk for a similar taste.
Still, water is definitely easier and more accessible than milk, and it's not a horrible ingredient for hot chocolate. It's best to try both to discover your personal favorite.