For the nigiri-style sushi: Cut 1 rice cereal treat bar in half lengthwise. Place 1 gummy fish on each piece lengthwise. Unroll the candy fruit strip and cut a 1/2-inch strip. Slice the strip in half lengthwise. Wrap 1 strip around each fish to secure it to the treat bar.
For the rolled sushi: Place the remaining fruit strip down on a cutting board. Top with the remaining cereal treat bar, pressing it down to flatten it and cover the fruit strip. Arrange the remaining 6 gummy fish in the center in a long line. Starting at the edge closest to you, roll the cereal bar and candy away from you to form a sushi roll. Gently press the candy into the cereal to secure. Using a sharp knife, cut into 4 pieces.