Usually, the client provides the food for their pets, especially if the pet has a specific diet. In addition to this, the client is responsible for the supplying of blankets/toys etc.
It is important for the well-being of the animal so that they can feel happy and comfortable with their Petsitter and not be disturbed. Of course, this can be arranged differently to better both parties but would need to be discussed in the initial messages if possible.
Remember that the integrated messaging system in Holidog is here to help you duscussing all the details in advance so that you do not have any surprises when you meet with your client/petsitter.