We're going to be there in a couple of weeks and I, too, have been looking at lunch spots in/near Grand Case. A few from my list (that I've never tried, simply have them on my radar for this trip): Restaurant Cool Heure - I think this is a lunch only bistro type place.
Le Claquettes Chausettes is a food truck serving tartines, burgers, and frites and regularly sets up at "Garage 7" , just down from Captain Frenchy's. The restaurant at Le Temps des Cerises hotel has lunch and you can use loungers on their beach. Java is a Mediterranean restaurant and beach club in Grand Case - the lunch menu looks quite good.
https://www.claquetteschaussettes-sxm.com/https://www.ltclaplage.com/restauranthttps://javasxm.com/
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