Preheat the oven to 350°F.
Mix the sugar and the water in a pot at a medium-high temperature and stir frequently to melt the sugar. Stir for about 30 minutes, or until the mixture has become thick, darker in color, and until the lumps are broken down.
Pour the caramel mixture into an 8-inch round pan and coat the entire inside of the pan. Set it aside and let it cool.
In a large mixing bowl, add the eggs, condensed milk, evaporated milk, whole milk, cinnamon, salt, and vanilla. Beat the ingredients with a hand mixer for about 2 minutes until everything is blended and the mixture is homogeneous.
Pour your ingredients mixture into the pan with the caramel layer under.
Place this pan into an ovenproof dish or baking pan and fill with hot water to about half-way up the sides.
Bake the dish for about 45 minutes in the oven. Turn off the oven and let it sit for another 15 minutes inside the oven.
Remove the dish and let it cool for 15 minutes, then place it into the refrigerator until it is cool.
To serve: run a butter knife around the edges of the flan and carefully turn it upside down onto a bigger plate.
Enjoy!