Sunny Sundays are the best. Strolling around a decent Sunday market is even better. The Pure markt (Pure market) is a seasonal market throughout several parks in Amsterdam. There’s great food, proper wine and all other things you need for a fancy picnic. Go with a bunch of friends and hang out in the park while enjoying all the nice stuff sold at the little stalls. In the meantime, you can buy all kinds of delicacies you’d like for the rest of the week.
Although some stalls are quite pricey, some offer decent deals as well. Just check out all of them before buying something you’ll regret later. Why? There are probably at least four stalls that sell olives, for example. Oh and make sure to find one of the stalls where they sell bottles of (mulled) wine, and you’ll have a good time for sure. My favorite edition is the one in Park Frankendael, but check out their website to find out where the next edition will be.