Add the chicken breast to a bowl and cover it in pickle juice. Cover and refrigerate the chicken for at least 2 hours, or overnight.
In a small bowl mix together the light mayonnaise, minced garlic, lemon juice, salt, and pepper. Cove and refrigerate until you're ready to use it.
Heat a grill pan over medium heat and coat with nonstick cooking spray.
Remove the chicken from the pickle juice and pat dry. Season the chicken with garlic powder, onion powder, and black pepper. Add the chicken breast to the grill pan. Cook for 3-4 minutes on each side (depending on the thickness of your chicken breasts). Once the internal temperature reaches 165 degrees F. it's ready.
Assemble the chicken sandwich by adding the chicken breast to the bun, red onion, and lettuce, then spread a tablespoon of the garlic aioli on the top bun.