When: On a sunny day in spring or autumn. Or in the shade during summertime.
Eat: As a traveller money can be rare sometimes. However you still want to experience local and typical foods for the area. A lot of bars and restaurants at the Cote d’Azur offer cheese plates most of the times very expensive ones… So why not do it yourself? A local store or even a normal supermarket has such a large variety of cheeses. So just buy a bunch, get a baguette at the “boulangerie” and sit at the beach. All you need is a large beach towel or blanket to sit on.
Drink: Pair it with some sparkling wine (lots cheaper than champagne but still delicious) or some local wine.
Do: Don’t forget sunscreen. It might not be that warm yet, but the sun is still strong.
My tip: Choose a beach with a public toilet. That way you can extent the lunch into dinner and further. A true backpacking experience.