For the pork tenderloin tacos: Preheat an outdoor grill to high heat on one side and medium-low heat on the other. Mix to combine the brown sugar, chili powder, coffee grounds, garlic powder, onion powder, paprika, 1 1/2 teaspoons salt and 1/2 teaspoon black pepper in a small bowl. Brush the pork tenderloins all over with the oil, then sprinkle over the dry rub on all sides.
Grill the pork on the high-heat side until it is nicely charred on all sides, 8 to 10 minutes. Move the pork to the medium-low heat side of the grill for indirect grilling. Cover the grill and continue grilling until an instant-read thermometer inserted into the center of the tenderloin registers 150 degrees F, 10 to 12 minutes longer. Remove from the grill and tent loosely with aluminum foil. Let the pork rest for 10 minutes. Thinly slice for tacos.
To warm the tortillas, heat the tortillas on the grill over low heat, turning once to brown them up a bit. Wrap them in foil to keep them warm until it's time to eat.
For the pineapple cucumber salsa: Stir to combine the pineapple, cucumber, jalapeno, lime juice, onion, cilantro, 1/2 teaspoon salt and 1/4 teaspoon black pepper in a large bowl.
For the assembly: To build each taco, place some pork onto a tortilla. Top with some shredded cabbage, pineapple cucumber salsa, sour cream and cilantro. Serve with lime wedges.
The rubbed and seasoned pork can be wrapped and refrigerated overnight.