Preheat oven to 350°. On a large baking sheet, toss together peanuts, coconut, and pistachios. Bake, stirring once or twice, until toasted and fragrant, 5 to 7 minutes; set aside.
Spray two large sheet trays (with sides) and the tines of 2 forks with cooking spray; set aside. Combine sugar, corn syrup, butter, vinegar, and salt in a large pot. Clip a candy thermometer to the inside edge of the pot and cook over medium-high heat, without stirring, until mixture reaches 300°, about 20 minutes. Meanwhile, combine peanut mixture and popcorn on 1 of the prepared sheet trays.
When sugar mixture reaches 300°, immediately remove pot from heat and set candy thermometer aside. Carefully pour hot sugar mixture over popcorn mixture, then use the prepared forks to toss together and coat well. (Work quickly, since the sugar mixture hardens as it cools.) Transfer popcorn to second prepared sheet tray and spread it out.
Set aside and cool completely, about 2 hours, then break into bite-size pieces. Serve immediately or store in an airtight container at room temperature.