Preheat a grill to high. Combine the beer, caraway seeds, coriander seeds, mustard seeds, onions, garlic and ginger in a large stockpot. Add the bratwurst. Place the pot on the grates of the grill and bring to a simmer. Simmer the sausages, about 5 minutes.
Remove the pot from the grill and let the bratwurst sit in the liquid for about 30 minutes. Transfer the brats to a platter or cutting board.
Brush the bratwurst with the canola oil and grill until the casings are crisp and golden brown and the brats are warmed through, 4 to 6 minutes per side. Keep warm until serving.