Prep all ingredients as listed above.
In a medium bowl, combine tuna, mayonnaise, Dijon mustard, olives, parsley, salt, and black pepper. Mix until well combined.
Optional: Lightly toast the sub rolls for extra texture.
Layer the bottom half of each roll with shredded lettuce, sliced tomato, sliced red onion, and the tuna mixture. Add extra olives if desired.
Place the top half of each roll on the sandwich and cut each sandwich in half.
In a pitcher or large glass, combine all the ingredients together. Stir well and let sit for 5 minutes to allow the chia seeds to expand. Stir again and garnish with fresh mint.
Serve the sandwich with carrot sticks, hummus, pickle spears, chocolate chip cookie, and sparkling chia fresca.