No. 4 Xinjiekouwai Street, Xicheng
Hai Dian District
8 am - 12 pm
Great sandwich shop with several locations around the city. Very affordable (around 50-70 RMB) and they also provide wi-fi.
Tube Station Sandwich has another location near Dong Zhi Men as well:
No.18 Xinzhongjie, Dongcheng - Phone: 010 - 8447 3949