Place 3/4 cup sugar, 2 teaspoons cinnamon, 1 teaspoon nutmeg, and 1 teaspoon vanilla extract into a gallon size resealable plastic bag. Seal the bag and shake to blend the sugar mixture. Add the sweet potato sticks, seal the bag, and turn to evenly coat the potatoes with the sugar mixture.
Pour the canola oil into a deep fryer and heat to 375 degrees F (190 degrees C). Add the sweet potatoes, and cook until golden, about 10 minutes. Drain on paper towels, then place on a serving plate.
Place the remaining 1/2 cup sugar, 1 teaspoon cinnamon, 1 teaspoon nutmeg, and butter into a pan. Warm over medium heat until butter is melted; drizzle over the sweet potatoes.