Prep all ingredients per the instructions above.
In a bowl, whisk together olive oil, lime juice, garlic powder, cumin, chili powder, and cilantro. Add the chicken and coat well with the marinade. Refrigerate for at least 30 minutes.
Make the guacamole: In a bowl, mash the avocado until smooth. Stir in cilantro, garlic, cumin, and lime juice. Refrigerate until ready to serve.
Preheat a grill or grill pan to medium-high heat.
Saute the chicken in a nonstick pan over medium heat to an internal temperature of 165°F (74°C). Remove from heat.
Warm the tortillas: Heat a dry skillet over medium heat. Warm each taco shell for 20 seconds per side until soft and pliable.
Assemble the tacos by filling the shells with chicken, lettuce, tomato, onion, and cheese.
Pour sparkling water over lemon slices and chia seeds. Stir and let sit 2 - 3 minutes for the chia to bloom. Serve with ice if desired.
Serve tacos with tortilla chips, guacamole, and lemon chia sparkling water.