which is the best supermarket or place near capital hotel for clothes in Beijing

Close to your hotel, it is hard to find some good places to buy clothes. I only know there is a Dafang Department Store along the Qianmen East Street and Aohua Clothes Market. But I do not think you can find the suitabla clothes there.
In my opinion, your hotel is very close to Wangfujing and you can go there to have a look. I am sure you can find different kinds of shopping malls.