These are my personal tips -based on experience and research- for a great experience in Rotterdam! This resulted in a good list of tips! You can click on the bold text to get to the Google Maps location of the establishment.
Het Eethuisje van Delfshaven Original Dutch ‘cuisine’. Cuisine? Well, Dutch food, real Dutch food. Wouldn’t call it cuisine, really, but good if you want to try.
In de Keuken van Floris Not cheap, but a once in a lifetime experience. 8 or 9 courses, an evening full of culinary entertainment. One big space contains both the kitchen and the restaurant, you are literally in the kitchen!
Stroopwafels (syrup waffels), of course. Buy a hot one at the Market.
Kroketten (goulash croquettes). You can buy them everywhere, for example at the Kroketloketin the Markthal.
Zoute drop (salty licorice). Strange, but nice. Buy them at any supermarket.
Haring (herring)! Not for the faint-hearted, eaten raw. You can buy them at them at the Marketon Tuesdays and Saturdays. Look for the red, white and blue flags, take it by the tail and let is slide in!