For talisker, most/all the rowers will have freeze dried food (store bought or self-made). The boats have a desalination plant (the boats have solar panels) so they do have fresh water, but only enough for drinking/eating, they would normally jump into the ocean to rinse themselves.

yes, they bring they own electronic devices, but you do have to be judicious in usage due to the aforementioned solar panels not being very big. Here's a picture (to be clear, this one used for the talisker, the ABC articles have a better image of the one specifically used by the brothers):

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSmNq8z...