How to Make It
Whisk together water, rice vinegar, sugar, and salt until dissolved. Place pork in a large ziplock plastic freezer bag; pour in brining mixture. Chill 2 to 3 hours.
Preheat grill to medium-high (about 450°F). Remove pork from brining mixture; discard brining mixture. Pat pork dry with paper towels; rub with oil, thyme, and cracked peppercorns.
Place pork on grate; grill, uncovered, turning occasionally, until a meat thermometer inserted in thickest portion registers 140°F, 20 to 22 minutes. Remove from grill, and let stand until temperature registers 145°F, about 5 minutes.