Pour the water into a large pot, and stir the sugar and 1/2 cup salt together until dissolved. Place the ears of corn into the pot, and allow to soak at least 30 minutes but no longer than 8 hours.
Preheat an outdoor grill for high heat, and lightly oil the grate.
Remove the corn from the soak and grill the ears, turning every 2 to 3 minutes to cook the kernels on all sides. Brush the grilled corn with butter, and season to taste with salt and pepper.
