Combine the sugar, seasoning salt, chili powder, paprika, pepper, and cayenne pepper in a medium resealable bag. Seal and give it a good shake. This will be the spice rub for the flank steak.
Cut up the zucchini, onion, and peppers. Place the vegetables with 1 tsp. of oil in another medium freezer bag. Seal and shake to combine.
Trim the fat from the flank steak and place it in a large resealable freezer bag. Add the ginger ale and soy sauce. Remove the excess air from the bag. Seal.
Staple the 3 bags together above the seals. Freeze.
Remove the flank steak from the marinade and pat dry. Use the prepared spice rub and liberally coat the flank steak, shaking off the excess. Allow the meat to rest at room temperature for about 15 minutes.
Wrap the vegetables in two layers of heavy-duty aluminum foil. Sprinkle with 1/2 tsp. of seasoning salt. Seal the packet tightly.
Prepare the grill to high heat. Oil.
When the meat has rested and the grill is hot, place the steak on the oiled grill grate.
Add the vegetable packet to the grill as well.
After about 4 minutes, flip the steak and veggie packet. Cook for an additional 4-6 minutes to medium or to desired doneness.
Allow the steak to rest after cooking for 5-10 minutes before slicing. Serve with vegetables.