For the rice: Add the sushi rice, rice vinegar, sugar, 2 cups water and 1 tablespoon salt to a medium saucepan, mix to combine and bring to a boil. Reduce the heat to a simmer, cover and cook until the rice is tender and the water is completely evaporated, about 15 minutes. Remove from the heat and let sit for 10 minutes, then fluff with a fork.
For the meat: Meanwhile, mix the soy sauce, granulated sugar and sambal olek in a medium bowl. Add the meat slices and toss to coat. Let sit for 15 minutes at room temperature.
Heat the oil in a large nonstick skillet over medium heat. Add the meat and cook, untouched, until starting to turn golden, 1 to 2 minutes per side. Transfer to a plate.
Lay a strip of nori on a flat work surface. Place a musubi mold on top and in the center. With wet hands, press one-sixth of the rice into the mold, then top with a piece of meat. Wrap the nori strip around the rice and meat and seal with a little water. Repeat with the remaining rice, meat and nori. Serve immediately.