Like pets in real life, pets in the game need to be fed in order to keep them awake, happy, and active! Without snacks, your pets will fall asleep and will not perform their tasks.
To feed your pets, tap on the pet that is sitting on the left side of the spin button to load up the pet menu. Once there, choose the pet you want to feed and tap on the pet treats button found on the bottom right corner of the screen.
Multiple snacks can be used on a pet at the same time to activate it for longer periods of time.