Sheraton Beijing Great Wall from Terminal 2 at 12am

Well, see whether if you can catch the airport shuttle bus line 1. The last schedule is at 01:00 am.
If you can, take it and get off at Liangmaqiao Station. The ticket fare is CNY 18 per person. Then walk north around 350 yards to find the hotel.
If you miss bus, you need to take a taxi. The cab fare is CNY 90 to 100 in the night.