Combine ketchup, apple cider vinegar, and molasses in a small saucepan. Warm over medium heat, stirring occasionally, until bubbling and slightly thickened, about 3-5 minutes. Set aside.
Slice the smoked ham into thin slices, about 1/4 inch thick; set aside. If using cheese, lay slices on the ham to melt later.
In a small bowl, mix melted butter with minced garlic. Brush this garlic butter mixture on the cut sides of the buns, then place them cut-side up on a baking sheet. Toast in a preheated oven at 175°C (350°F) for about 5 minutes until golden and fragrant.
Spread a generous layer of the warm BBQ sauce on the bottom halves of the toasted buns. Layer slices of ham over the sauce, then spoon more BBQ sauce on top of the ham, ensuring everything is coated well.
If using cheese, place slices over the ham now, so it melts in the oven. Cover with the top halves of the buns, pressing down gently.
Brush the tops of the assembled sliders lightly with the garlic butter for extra flavor and a shiny finish. Place the sliders back on the baking sheet.
Cover with foil and bake in the oven at 175°C (350°F) for 15-20 minutes, until the sauce is bubbling and the buns are golden. Remove the foil in the last 5 minutes if you want a slightly crisp top.
Once done, remove from the oven and let the sliders rest for 5 minutes. This helps the juices settle and makes slicing easier.
Slice the sliders apart carefully with a sharp knife, revealing the gooey, smoky ham inside. Serve warm, with extra BBQ sauce on the side if desired.
