Place the desired number of tenderloins in a slow cooker along with a 1/2 cup of beer or stock per pound of meat. (Leftovers are delicious, so remember to cook extra!)
Cook for 6-8 hours on low or 3-4 hours on high.
Pour off liquid, reserving a cup or so of it, and shred the meat. I find this is easiest to do with two dinner forks–on a dinner plate for easy clean up.
Place meat back in the slow cooker and mix in barbecue sauce, coating to your liking. If desired, you may stir in some of the reserved cooking liquid and thin to your desired level of sauciness.
Cook on low to heat through, another 30 minutes or so.
For grilled sandwiches, lightly cover the bottom half of the hamburger roll with your choice of cheese. Top with the shredded meat and a spoonful of barbecue sauce. Sprinkle more cheese over the sauce, and put on the top of the roll.
If using a panini grill, cook for three minutes or until the bread is golden and crusty. You may also grill as you would a grilled cheese sandwich, weighing down the roll with a cast iron skillet or heavy pot to achieve the same squished-but-crispy effect. When cooking on the stovetop, grill over medium heat for approximately three minutes per side or until the bread is golden and the cheese is melted.
Serve with additional barbecue sauce and a salad or veggies of choice.