Combine 1 cup granulated sugar and 2 teaspoons ground cinnamon in a shallow dish, whisking until evenly distributed. Set aside near your frying station.
In a large saucepan, combine 1 cup water, 6 tablespoons butter, 1 tablespoon sugar, and 1/4 teaspoon salt. Bring to a full rolling boil over medium-high heat, stirring occasionally.
Remove from heat and add all 1 cup sifted flour at once. Stir vigorously for 30-60 seconds until no dry flour remains and the mixture forms a cohesive ball. Return to heat and cook 30 seconds more, stirring constantly.
Transfer the hot dough to a stand mixer fitted with the paddle attachment and let cool for 5-10 minutes until warm but not steaming (140-150°F/60-65°C).
Add eggs one at a time, beating on medium speed until fully incorporated after each addition. Add vanilla extract with the final egg. Scrape down the bowl between additions.
Pour 6 cups of oil into a heavy pot to a depth of 2-3 inches. Heat to 360°F (182°C) while transferring the dough to a piping bag fitted with a large closed star tip.
Once the oil reaches temperature, pipe 5-6 inch lengths of dough directly into the oil, using kitchen scissors to cut. Fry 3-4 at a time for 2-3 minutes per side until deep golden brown.
Remove fried churros with a spider strainer and immediately roll in the cinnamon sugar mixture to coat evenly while still hot.
Repeat with remaining dough, maintaining oil temperature between batches. Serve immediately while warm and crispy with chocolate sauce, caramel, or dulce de leche for dipping.