Place potato cubes into a small saucepan. Fill with just enough water to cover the tops.
Bring to a boil over medium heat; cook for 4-5 minutes, partially covered, until potatoes are nearly cooked but still slightly firm. Remove from the heat; cool slightly.
To prepare the spice mix: mix together the garlic salt, chili powder, salt, pepper, cumin, paprika and crushed red pepper. Set aside.
In a separate bowl, combine the honey and cider vinegar and set aside.
Add chicken to a medium bowl; lightly drizzle with olive oil and toss with half of the spice rub. Repeat with the potato pieces and onion: drizzle with olive oil and toss with remaining spice rub.
Put the chicken, sweet potato, and onion onto the pre-soaked bamboo skewers. Brush with half the honey glaze.
Preheat the grill on medium heat; grill the chicken skewers for 8 minutes, turning often.
Remove from the grill and brush the skewers with the rest of prepared honey glaze as desired. Serve immediately.