Whisk egg yolks and sugar together until light in color and fluffy.
In a small pot or saucepan, heat the heavy cream and coconut milk. Do not boil, simply hot enough to get warm and steam but NOT boil.
Pour the heated milk slowly into the bowl of egg yolks and sugar. Whisk continuously while pouring so as not to turn your eggnog into scramble.
Add and stir in the vanilla, nutmeg, cinnamon. Chill in the refrigerator until you are ready to serve or serve immediately as a hot beverage. ** (SEE NOTES)
If serving spiked add alcohol right before serving.
Notes
** Add the water if you would like it to be a thinner consistency. We like ours rather thick but if you'd like to thin it out you can add as much water (up to 1/2 cup) as you'd like.