Whisk water, soy sauce, olive oil, lemon juice, brown sugar, and garlic together in a large glass or ceramic bowl. Add chicken tenders and toss to evenly coat. Cover the bowl with plastic wrap and marinate in the refrigerator for at least 3 hours.
Preheat an outdoor grill for high heat and lightly oil the grate.
Remove chicken from the marinade and shake off excess. Discard the remaining marinade.
Place chicken on the grill and reduce heat to low. Cook for 1 minute, then turn and grill until no longer pink in the center and the juices run clear, 4 to 6 minutes. An instant-read thermometer inserted into the center should read at least 165 degrees F (74 degrees C).