Preheat a grill to medium high. Make the salsa: Combine the tomatoes, lime juice, sugar and 1 teaspoon salt in a small microwave-safe bowl. Microwave 2 minutes, then stir in the cilantro, red onion and jalapeno; set aside.
Toss the corn with the vegetable oil in a large bowl; season with salt and pepper. Form the beef into four 1-inch-thick patties; season with salt and pepper. Lightly brush the grill grates with vegetable oil. Grill the corn, turning occasionally, until marked and tender, about8 minutes. Meanwhile, grill the burgers about 4 minutes per side for medium rare. Toast the buns on the grill.
Sandwich the burgers on the buns with the guacamole and salsa. Serve with the corn.