Line a rimmed baking sheet with parchment paper and lightly coat with cooking spray; set aside.
In a medium saucepan, combine the sugar, water, corn syrup and salt. Bring to a rapid simmer over medium-high and cook until deep golden, about 20 to 25 minutes. Remove from heat. Stir in the butter, baking soda and pistachios (the mixture will foam). Continue to stir until the mixture is no longer bubbling and the caramel is smooth, about 1 minute.
Transfer to the prepared baking sheet and spread with a rubber spatula that has been sprayed with non-stick cooking spray. Let cool until firm, about 15 minutes. Break into pieces. The brittle can be stored in an airtight container at room temperature for up to 3 weeks.