Special equipment: 12 wooden pop sticks
In a deep-fryer or heavy-bottomed pot, heat enough canola oil to come halfway up the sides of the pot, to 375 degrees F.
In a medium-sized, heavy bottomed saucepan over medium heat, add the caramels, butterscotch chips, milk and vanilla. Cook, stirring frequently with a rubber spatula, until well incorporated, melted, and smooth, about 8 to 10 minutes. Keep warm.
In a medium bowl, whisk together the eggs, seltzer, 1 1/2 cups of flour, and cream of tartar. Skewer the apples onto wooden sticks. Dredge the apples, first in 1/2 cup flour, and then into the batter. Fry the apples, in batches, in the deep-fryer until crispy, about 2 to 3 minutes on each side. Drain on paper towels. Pour the caramel sauce into a small bowl. Dust the apples with cinnamon sugar and serve with the caramel sauce.