Skewer the hot dogs and cheese on sticks, hot dogs on the bottom and cheese on top. Place in the fridge to keep cold.
In a bowl, whisk together the flour, salt, and sugar. Mix in the egg and milk until thick and smooth. Pour into a tall cup and place into the fridge. Pour the panko onto a shallow plate that you will be able to roll the corn dog in.
In a deep fryer or a deep wide pot, heat up the oil (enough so that the hot dog will float) over medium high to medium heat, until it reaches 350°F. When the oil is almost at temp, take the skewered dogs from the fridge and dip into the batter, making sure it is completely coated.
Roll the coated corn dog in panko, making sure that the panko coats all of the batter, using your hands to gently press it on if needed.
Carefully add the coated corn dog to the oil and fry for 3-4 minutes or until golden and crispy, turning as needed. Remove from the oil and let rest on a wire rack.
Roll or sprinkle the corn dog with sugar and drizzle on mustard and ketchup. Enjoy hot!