Place the chicken cubes in a medium glass bowl or heavy-duty resealable bag.
Pour the dill pickle juice and milk over the chicken. Seal or cover and refrigerate for 30 minutes.
In a small mixing bowl, combine the powdered sugar, salt, black pepper, garlic powder, onion powder, and smoked paprika. Whisk to remove clumps.
Drain the chicken thoroughly using a colander. Discard the marinade.
Pat the chicken pieces dry with paper towels to ensure proper searing on the grill.
Transfer the chicken to a clean bowl and toss with the prepared spice blend until every piece is evenly coated.
Preheat a grill pan or cast-iron skillet over medium-high heat. Once hot, lightly brush the surface with the oil.
Place the chicken nuggets in the pan in a single layer, ensuring they are not touching.
Grill for 3 to 4 minutes per side until lightly charred and the internal temperature reaches 165°F (74°C).
Remove from heat and allow to rest for 2 minutes before serving.