I used cider vinegar instead of wine. Great!
Replacing red wine with cider vinegar alters the chemical profile of the braising liquid entirely. Wine introduces residual sugars and complex tannins that mellow during extended moist heat. Vinegar supplies a sharp, direct acetic acid that does not soften in the same manner. Reduce the added vinegar quantity by half if substituting, or balance the pH with a pinch of sugar. Pork tenderloin contains very little intramuscular fat and dries out quickly if cooked past 145 degrees Fahrenheit internally.
Long cooking times break down connective tissue, but lean cuts behave differently than shoulder roasts. Liquid should submerge no more than halfway up the meat to prevent boiling instead of braising. Monitor the internal temperature using an instant-read thermometer inserted into the thickest part. Remove the roast immediately when it reaches the target temperature. Rest the meat for ten minutes before slicing to allow internal juices to redistribute evenly throughout the muscle fibers.
The remaining liquid in the crockpot concentrates flavors from the onion soup mix, garlic, and soy sauce. Skim off any surface fat using a wide spoon before serving this au jus alongside the sliced meat. Pair the pork with plain starches like mashed potatoes or buttered noodles. These neutral bases absorb the salty, savory liquid effectively without competing against the garlic and aromatics.