Line a baking sheet with aluminium foil and set an oven safe wire rack on top. Lay strips of bacon on the rack and bake for 15 minutes, until starting to cook but not crispy or fully done. Remove from oven and reduce heat to 350 degrees. Carefully drain bacon fat and replace aluminum foil when cool enough to handle.
Meanwhile, whisk the lager, Worcestershire, dry mustard, and garlic salt in a large pot. Poke the brats a few time with the tines of a fork and add to the pot. Bring to a boil. Reduce heat and simmer for 15 minutes, flipping the brats once halfway through.
Remove brats from liquid and let cool until safe to handle.
Spiral a slice of bacon around each brat and use toothpicks to secure. Place back on the wire rack and bake for 15-20 minutes, until bacon is fully cooked, flipping once halfway through.
Combine the mayo, whole grain mustard, and Dijon mustard in a small bowl. Cover and place in fridge until ready to serve.
Serve brats on toasted buns with Swiss cheese, sauerkraut, pickles and a spoonful of mayo mustard mixture.