Preheat oven to 375'
Lightly coat a medium saute pan with vegetable spray and the garlic, onion, sweet potato, bell pepper, chili powder and cumin. Saute for about a minute or two to toast the spices. Add the water and stir. Cook on medium heat about 8 to 10 minutes or until the water has evaporated and the vegetables are tender. Cool and place in a large bowl. Add the cilantro, turkey and cheddar cheese and toss well to blend.
Melt butter in microwave. Keep phyllo dough on a sheet pan and cover with a dampened kitchen towel or paper towel. Working with one sheet at a time, lightly brush butter across the sheet and fold in half lengthwise. Place a tablespoonful of the filling about 1/2" from the bottom. Fold the bottom up over the filling. Lightly brush the dough above the filling with butter. Grasping the corner with the filling gently fold over the the opposite side to form a triangle. Now, fold the triangle up onto the dough, then fold left (or right) and up again and continue until you reach the top of the dough. If needed lightly dab with butter to seal the edge. Place on a sheet pan that has been covered with parchment paper. Repeat this process until the dough and filling are used. Brush the tops of each empanada with a little butter so it will brown nicely. Bake for 20 to 25 minutes or until they are golden brown and crispy.
If you are going to freeze any don't brown them all the way and remove from oven after about 15 minutes. They can be cooled and frozen at this point to be reheated in the future.