Remove pork tenderloin from the packaging and remove excess fat and any silver skin.
To a mixing bowl add water, sugar and salt. Whisk until both are dissolved.
Smash the garlic cloves, remove the skin and add to the water along with the black peppercorns.
Add the pork tenderloin, cover and refrigerate for 8 hours.
Remove the pork from the brine 30 minutes before cooking. Discard the brine.
If cooking in a pan, preheat over medium heat for 5 minutes.
Add olive oil to the pan and add the pork tenderloin. Cook for 3 minutes on each side (four sides) for a total of 12 minutes. Take the pan completely off the heat and set on a cold burner, cover and let the pork tenderloin continue cooking via residual heat for 10 minutes.
Remove from the pan, slice and serve.
If you're grilling, preheat the grill on high for 10 minutes. Place the pork tenderloin on one side. Turn the heat down to low on the opposite side the pork is not on. You will have a hot and warm side.
Close the lid and cook for 90 seconds. Do this for all four sides. For a total cook time on the hot side of 6 minutes.
Place the pork tenderloin on the warm side on it's flatter side. Close the lid and cook for 4 minutes.
Flip and cook on the other flatter side for another 4 minutes with the lid closed.
Remove the meat and cover tightly with foil. Allow to rest for 10 minutes befores slicing and serving.