Make sure the arroz con leche is completely cooled and refrigerated until cold and firm. Cold rice pudding is much easier to shape.
Scoop 2 tablespoons of chilled arroz con leche and roll it into balls using your hands. I used a cookie scoop to make it easier and more uniform. You should end up with about 16 balls. Place the balls on a parchment-lined baking sheet and place in the freezer for 10-15 minutes while you set up your dredging station.
In a shallow bowl, place all-purpose flour and cinnamon powder, use a fork to mix until combined. In another shallow bowl place your two eggs and beat them together. In your third bowl, place your finely crushed Cinnamon Toast Crunch cereal.
Roll each arroz con leche ball in the cinnamon flour mix, shaking off the excess. Dip it into the beaten egg and make sure it's completely coated, then transfer the ball and coat thoroughly with the crushed Cinnamon Toast Crunch.
Place the breaded balls in the freezer for 15 minutes while you get ready to fry them.
Add enough neutral frying oil to a deep, heavy-bottomed pot to submerge the sweet arancini. Heat the oil to 350°F.
Carefully lower a few sweet arancini into the hot oil without overcrowding the pot. Fry for about 2–3 minutes, turning as necessary, until the outside is crisp and golden brown.
Transfer the fried arroz con leche balls to a paper towel-lined plate or wire rack. Allow them to cool for a few minutes before serving warm.
Serve them hot and drizzle with condensed milk if desired.