Hannekes Boom is one of the nicest waterfront café in Amsterdam to have a beer when it's sunny. Close to Central Station, the place isn't crowded by tourists, but you need to be there early to get a seat.
A really lovely restaurant with terasse with lots of sun hidden in the west and close to Erasmus Park. It is a place where you will a lot of locals catching up. The food is always great and there is a super cosy and friendly atmosphere. The kind of place you actually want to keep a secret so don't tell anyone! ;)
Hidden in the greenery near Westerpark, the perfect hideaway from street noise can be found if you know where to look: a little farm called "De Buurtboerderij". Surrounded by a bunch of sheep and a happily decorated garden, the restaurant inside serves one fixed menu a week for a low price. The farm serves as community center as well and is run by volunteers — and you when you eat there! — and there are plenty of sweet people and animals to hang out with.