01 - Preheat your oven to 425°F (220°C). Line a large sheet pan with parchment paper or aluminum foil for expedient cleanup.
02 - In a medium mixing bowl, vigorously whisk together the cream soda, Dijon mustard, olive oil, apple cider vinegar, minced garlic, kosher salt, and black pepper to form the marinade.
03 - Place the pork tenderloin in a shallow dish or a resealable bag. Pour half of the prepared cream soda marinade over the pork, reserving the remaining half. Allow the pork to marinate for a minimum of 10 minutes, or up to 1 hour if time permits.
04 - While the pork is marinating, in a separate bowl, toss the sliced apples and onions with olive oil, ground cinnamon, salt, pepper, and thyme until evenly coated. Spread these seasoned fruits and onions in a single layer on the prepared sheet pan.
05 - Remove the pork tenderloin from its marinade (discard any used marinade) and position it in the center of the sheet pan, nestled amongst the apples and onions. Brush or spoon a few tablespoons of the reserved marinade over the pork. Transfer the sheet pan to the preheated oven and roast for 15 minutes.
06 - After the initial 15 minutes of roasting, baste the pork tenderloin with additional reserved marinade. Continue roasting for another 15 to 20 minutes, or until the internal temperature of the pork reaches 145°F (63°C) and the apples are tender and beautifully caramelized.
07 - Remove the sheet pan from the oven. Allow the pork tenderloin to rest for 5 to 10 minutes before slicing. Serve the sliced pork warm alongside the roasted apples and onions.