There are plenty of nice restaurants and beaches on Maui to watch the sunset, but if you're looking for a more unique experience, then look no further than Crater Road. Just off the side of the winding road is an amazing view point to set up a couple beach chairs and enjoy the sunset from a view that's arguably more impressive than any other location on Maui.
There is a chance you may get some cloud cover, but even if that happens, its still a great spot to relax and gaze over the open fields of green grass.
If you decide to make the journey, along with chairs, I would suggest bringing a blanket or two (hotel comforter), warm clothes, some hot coco or wine, and some cheese and crackers.
Park your car parallel to the road and setup your chairs on the grass on the opposite side of your car from the road. Typically there are a few cars coming down the Crater Road, but it doesn't really affect the serene atmosphere of the area.
If you're looking for dinner after sunset, head 10 minutes down the mountain to the Kula Lodge Restaurant.
For the specific google map location, see the google link here.