Crush celery seeds and caraway seeds with a mortar and pestle until ground.
Mix beer, brown sugar, dry mustard, onion powder, pepper, dill, and crushed seeds together in a bowl until brown sugar is dissolved.
Place brats into a large nonstick skillet over medium heat. Pour beer mixture over top and bring to a boil. Reduce the heat to low, cover, and simmer for 10 minutes.
Uncover and increase the heat to medium. Boil the sauce until it reduces to a thick, syrupy liquid, about 20 minutes. Tilt the skillet to roll brats in the sticky sauce until thoroughly coated. Transfer brats to a plate and cover to keep warm.
Add sauerkraut to the skillet and stir to combine with any leftover sauce; cook for 5 to 8 minutes. Transfer sauerkraut to a serving platter and top with warm brats.
