Slice the pineapple into rings about 1/2-inch thick.
In a mixing bowl, whisk together flour, sugar, baking powder, salt, and cinnamon.
Beat in the egg and milk until the batter is smooth.
Heat oil in a deep fryer or large pot to 375°F (190°C).
Dip each pineapple ring into the batter, ensuring it's fully coated.
Fry the rings in batches, turning once, until they are golden brown, about 2 minutes per side.
Remove with a slotted spoon and drain on paper towels.
While still warm, dust the fritters with a mixture of cinnamon and sugar.
Serve warm and enjoy!