If you need a place to sit with a nice cup of coffee, Sister Srey is just the place. Located right along the river, just past the Old Market, Sister Srey is a cute little cafe offering coffee, breakfast, and lunch.
The cafe is a great place to sit and relax while enjoying a cup of joe (although if you want air conditioning, fans are all you get here). While the menu has a couple local-type dishes, the vast majority is Western fare, serving up sandwiches and typical Western breakfast foods. For the non-meat eaters, the cafe serves a decent number of vegan- and vegetarian-friendly options.
On another note, to give back to the community, the cafe donates a percentage of its profits to the Hearts for Harmony Foundation, which aims to help locals.