I remember eating my first funnel cake at Disneyland when I was super young. Later, when I made my own funnel cakes, I remember eating my first one, and I tried hard to make them extra awesome because I was probably making someone else's first funnel cake and I remembered how awesome mine was. Make life easy for yourself and prep four or five disposable plastic piping bags with batter. Funnel cakes can be very messy to make, and this will totally help. —Duff
Add the oil to a deep pot and heat it over medium-high heat until it registers 375 degrees F on a deep-fry thermometer. Set up a work surface with 4 or 5 plastic piping bags, scissors, tongs, parchment paper, and a wire rack with parchment paper underneath.
In a big bowl, whisk the flour, baking powder, salt, cinnamon, and granulated sugar. Add the eggs and milk and whisk well. Get all the lumps out!
Fill all the piping bags with batter. Cut the tip off one bag and drizzle the batter straight into the hot oil in a swirly, crazy pattern. Toss the piping bag. When one side is golden brown, about 75 seconds, carefully flip the funnel cake with tongs and fry the other side, another 75 seconds. Fry the rest of the batter.
Drain the funnel cakes on the wire rack. While they're still warm and shiny, dust them with powdered sugar using a wire-mesh strainer. Serve immediately!