While driving back to our home in Murcia in our new motorhome (see here for that story) we overnighted in the pretty Spanish seaside town of Moncofa. They have a really handy aire de camping about 500m from the beach which we stayed at.
Just north of Moncafa (about 4 km) near the town of Nules is Platja Canina de Nules. The best beach I have ever encountered that allows dogs.
The beach was a mixture of stoney areas (like a lot of beaches of eastern Spain), but also lots of sandy bits – including in the water – so no need to wear flipflops in the water!
There are no bars or services, and there was only one other person swimming in the sea while his staffie looked on – too scared to go in the water!
If you are making the long journey up or down the AP7 and passing junction 49 then consider stopping here. Even without a dog, it is a nice quiet, undisturbed bit of beach great for a rest before continuing your journey.