Proceed through the "For Bella" mission until you get the "Find a way into the Weyland-Yutani Facility to save Bella" objective. Follow the stairs to a door, and exit the interior to enter a rocky exterior area with lava flowing down a cliff to your right. Run partway up the path ahead and look to the right across the chasm with a scoped weapon to find a box of donuts. Shoot them and they will disappear. Then, look to where your teammates are waiting to see a giant donut appear uphill. It will roll down, launch off the cliff, and explode in the lava.