Head out of Sara Park trailhead and follow the Watershed Loop. You'll come to a sign that shows Sonny's to the right.
Follow this trail and stay right the whole time. There are pretty good signs marking the trail you need to stay on. You'll see many other trails that connect into Sonny's so stay on the main trail to complete Sonny's at heart attack hill. This is where you connect back up with Watershed Loop for the ride back to the trailhead.