In a large bowl, combine the ground beef, ground pork, and ground lamb.
Add the grated onion, minced garlic, salt, black pepper, paprika, and cayenne pepper (if using).
Mix the ingredients thoroughly until well combined. If desired, add the sparkling water to the mixture for extra fluffiness.
Divide the meat mixture into 4 equal portions.
Shape each portion into a large, flat patty, about 1/2 inch thick.
Place the patties on a tray and refrigerate for at least 30 minutes to allow the flavors to meld.
Preheat your grill to medium-high heat.
Lightly brush the grill grates with vegetable oil to prevent sticking.
Remove the patties from the refrigerator.
Brush each patty lightly with vegetable oil on both sides.
Grill the patties for about 4-5 minutes on each side, or until they are cooked through and have a nice char on the outside. The internal temperature should reach 160°F (71°C).
Enjoy your meal!