You can go to Bac Ha market. It's great to attend the market meeting here where has many typical traditional cultures of Vietnam. You will have an occasion to enjoy the local cuisine. Besides, Sapa has some places having beautiful landscape like Ham Rong, Muong Hoa, Cat Cat village and so on. 22 days ago
My recommendation would be to book a trek with one of the local tribal ladies who will meet you in Sapa when you arrive and drop you off in time for your train back to Hanoi.
If you're going to experience Sapa, the best way is to get out and see some of the local villages like Ta Van and Ta Phin. If you're going to book a trek, you can do a google search and find contact details for the ladies who will take you out into the mountains. They usually can't write in English so you'll need to call them, but I can honestly say that this is the best way to experience Sapa and will only cost you between $10-$15 USD for the day. 21 days ago