Preheat the oven to 400 degrees F. Bake the sweet potatoes directly on the oven rack until tender, about 50 minutes. Let cool completely.
Coat a baking sheet with cooking spray. Peel the sweet potatoes, transfer to a large bowl and mash. Stir in 1 1/2 cups crushed chips, the onion, butter and egg. Add 1/2 teaspoon salt, and pepper to taste; stir until combined.
Spread the remaining 2 1/2 cups crushed chips in a shallow dish. Scoop about 1 tablespoon of the sweet potato mixture into your hands and shape into a small 1-inch-long cylinder. Repeat to make about 36 cylinders. Roll in the crushed chips to coat on all sides and arrange on the prepared baking sheet; spray with cooking spray. Bake, rotating the pan halfway through, until crisp and golden, about 30 minutes. Season with salt.
Meanwhile, mix the mayonnaise and Sriracha in a small bowl. Serve on the side for dipping.