Pour cold water into a large pot. Stir in sugar and 1/2 cup salt until dissolved. Place corn into the pot and allow to soak for at least 30 minutes but no longer than 8 hours.
Preheat an outdoor grill for high heat and lightly oil the grate.
Cook corn on the preheated grill, turning every 2 to 3 minutes, until slightly charred on all sides. Brush corn with butter; season with salt and pepper.