In a gallon size re-sealable bag, add the chicken, grapefruit soda, orange juice, rice vinegar, Dijon, olive oil, lemon pepper and granulated garlic. Place in the refrigerator and marinate for 2 hours.
Preheat the grill to medium-high over direct heat.
Remove the chicken from marinade and add to the grill. Cook for 8 to 10 minutes, flip over and cook until the internal temperature is 160 degrees F, an additional 5 to 6 minutes. Remove from the grill, cover lightly with foil and allow to cool.
Split the baguettes in half, remove any excess bread from inside the top half and lightly toast on the grill.
In a small bowl, combine the whole-grain Dijon and marmalade. Spread this mixture on the toasted bread halves.
Slice the chicken breasts into 1/2-inch pieces on the diagonal and place on the bottom half of the bread. Top evenly with the cheese and lettuce. Top with the top half of the baguette and slice on a diagonal to serve.