In a large mixing bowl, combine the ground pork, ground beef, cumin, black pepper, and salt.
Add the cold water and optional sparkling water.
Knead the meat mixture thoroughly for several minutes until it becomes sticky, smooth, and elastic. Proper kneading is essential for authentic kebapche texture.
Cover the bowl and refrigerate for at least 2 hours, preferably overnight, to deepen the flavor and improve texture.
Wet your hands lightly with water and shape the meat into long sausage-like cylinders about 5–6 inches long.
Place the shaped kebapche on a tray and refrigerate another 20–30 minutes before grilling.
Preheat a charcoal grill, gas grill, grill pan, or cast iron skillet over medium-high heat.
Lightly oil the grill grates and cook the kebapche for about 4–5 minutes per side until browned, lightly charred, and fully cooked inside.
Serve hot with fries, grated sirene cheese, chopped onions, Shopska salad, lyutenitsa, mustard, or grilled vegetables.