this depends on what your definition of fun is.

Fun on Sunday can range from a walk to the Joordan / stroll on the canals / drinks at that bar on spui with the cat (someone help me here, I forgot what it's called) . That bar is the only place in AMS that makes Cosmo's and other things you'll find at gaybars stateside. I usually run into a lot of folks from the US there for that reason. Expats and visitors.

On the other scale, there's SOS @ Kerkstraat (very dutch).