Preheat oven to 220ºC. Line a pan (baking tray with lip) with nonstick foil.
Pour beer into a skillet over high heat. Pierce each bratwurst in several places with a fork and place in skillet with beer. Heat until very hot, but not boiling. Reduce heat and simmer gently for 15 minutes, turning bratwursts while cooking. Remove bratwursts from skillet and let sit until cool enough to handle. Discard beer.
When cooled, cut each bratwurst in half and wrap with one bacon half.
In a mixing bowl, stir together brown sugar, cayenne pepper and dry mustard until well combined. Coat each bacon-wrapped bratwurst in sugar mixture.
Lay coated bratwursts in the foil-lined pan with the seam of bacon firmly down so it won’t curl. Bake until bacon is crispy turning as required.
Remove to paper towels to drain briefly, then arrange on a serving platter.
Serve hot with a variety of mustard and toothpicks for dipping.