You can reheat hot chocolate the next day.
If you have leftover hot chocolate you can place the leftover hot chocolate in the refrigerator and then reheat it in the microwave.
To reheat the hot chocolate you can place a microwave safe cup in the microwave with the hot chocolate and heat the hot chocolate for a few minutes until it's hot enough.
Hot chocolate can be reheated in the microwave until hot but not boiling.
For leftover hot chocolate, allow the hot chocolate to cool to room temperature, then refrigerate for up to 3 days.
You can also reheat the hot chocolate on the stove until it's hot and steamy but not boiling.
You don't want the hot chocolate to become boiling but just steamy.
The shelf life of hot chocolate should be about 3 to 5 days in the fridge, with a cumulative stay in the danger zone of no longer than 2 hours.