Prepare a baking sheet lined with parchment paper or a silicone mat and sprayed with cooking spray.
Set a large, heavy pot over high heat. Add the sugar, beer, corn syrup and vanilla and mix together. Bring to a boil, reduce the heat to a simmer and cook until the sugar has dissolved completely and the liquid reaches a temperature of 305 degrees F (a small amount dropped in ice water will set and form a strand when dropped in). Remove from the heat and mix in the peanuts and pretzels. Carefully pour onto the prepared baking sheet and allow the beer brittle to cool completely on the counter top. Break the candy into pieces once cooled.