My trusty water bottle. I take it with me everywhere. It saves me tons since I don’t need to buy water and it’s better for the environment. SFwater.org has a map of water tap locations in the city. Drink water, it’s good for you and free!
I’d argue that SF has the best tasting water in the country. Drink up!
If you want to check out other free things in SF, or free things to do in SF, check out My Frugal Life and Free By District on this website.