Preheat oven to 425 F.

In skillet over medium-high heat, brown ground meat. Stir in taco seasoning, tomato sauce and beans; set aside.

Lay out six 12-inch aluminum foil pieces; spray each with nonstick cooking spray.

In center of each foil piece, place 1 cup sweetpotatoes, 1 teaspoon butter, 1/8 teaspoon salt, 1/4 cup spinach, 1/3 cup taco meat and 1/4 cup cheese.

Fold foil sides in over mixture; fold top and bottom foil ends inward and seal.

Place packets on rimmed cookie sheet; bake until sweetpotatoes are tender, about 25 minutes.

Serve with sour cream or guacamole, if desired.