For the barbecue sauce: Heat the bacon grease in a saucepan over medium heat. Add the red onions, and sweat until translucent. Add the garlic; cook an additional minute. Add the garlic powder, smoked paprika, salt, mustard powder and black pepper, and toast the spices until fragrant and deep maroon in color, 1 minute. Whisk in the cherry cola, red wine vinegar and ketchup until combined. Bring to a boil and cook until the sauce has reduced to 2 cups and coats the back of a spoon, about 10 minutes. Remove from the heat, let cool slightly, and then puree in a blender until smooth. (Extra sauce can be kept refrigerated up to 1 week.)
For the shrimp: Preheat a cast-iron skillet or griddle over medium heat.
Sprinkle the shrimp with salt and pepper. Insert a jalapeno slice into the "spine" of each shrimp (where it's been deveined) and then wrap tightly with a half piece of bacon to keep the jalapeno in place. Secure with toothpicks.
Place the shrimp, seam-side-down, in the skillet and cook, turning occasionally, until the bacon is crisp and the shrimp are just cooked through, 5 to 6 minutes.
Serve the shrimp with the barbecue sauce for dipping.