Fill a saucepot with 2 quarts of water and start warming up the grill.
Peel sweet potatoes and cut into one-inch medallions. Option to leave potatoes whole, note cooking time will be longer.
Rinse the potatoes and place them in the saucepot. Make sure the potatoes are fully submerged in water, so add more water if needed.
Bring water to a boil and cook the sweet potatoes for about 15 to 20 minutes. We are looking for a fork-tender for the potatoes, but not overcooked. This step could be done the day before the event. Make sure to cool the potatoes down by placing them on a plate and then in the refrigerator uncovered for about 30 minutes.
While potatoes are cooking, mix all the other ingredients in a bowl. We are going to
Once potatoes are just fork-tender, remove potatoes from the pot and place on a paper towel-lined plate or baking sheet. We want to absorb some of the excess liquid from the potato before transferring them to the grill.
Place the potatoes on the grill. We want a medium heat area. Too hot will scorch them, and too low will not give the potatoes grill marks.
Cook side of the potatoes for about 5 minutes, then turn the potatoes 90 degrees. Cook for another 5 minutes. If potatoes are marking faster than 5 minutes feel free to adjust your cooking time.
Turn the potatoes over to the other side.
Take the sugar and spice mixture and brush the potatoes with the mixture. Let potatoes cook for another 5 minutes.
You can opt to flip the potatoes to caramelize the mixture onto the medallions, but you will still get a nice sticky covering on the potatoes.
Remove from the grill and serve as a side dish or as the main entree.