Combine chopped cilantro, minced garlic, lime juice, olive oil, salt, pepper, sugar, and water. Stir to combine.
Place steaks in a large ziplock bag and add marinade. Reserve about a ½ cup to use for basting the steaks when they are grilled.
Seal bag, squeezing out excess air.
Place in the refrigerator and allow steaks to marinate overnight. Turn bag once or twice during marinating time to ensure steaks are completely coated with the marinade.
Remove steaks from bag and discard marinade in the bag.
Grill steaks on a barbecue grill to desired doneness, basting with reserved marinade. Cook time will vary depending on the thickness of the steaks.
Remove from heat when steaks reach an internal temperature of 130℉, for medium doneness.
Allow steaks to rest for 5-10 minutes before serving to allow juices to redistribute.
Notes
You can easily halve the marinade if you aren't cooking up a lot of steaks.