Small pets like guinea pigs, hamsters, and rabbits require specialized diets to stay healthy. Guinea pigs should eat hay, pelleted food, and limited vegetables and fruits to avoid digestive issues. Hamsters do best on pelleted diets but loose seed mixes are okay if they don't pick favorites. Rabbits need constant access to hay and grass as their digestive systems require fiber, with small amounts of pellets and greens as supplements. All small pets benefit from fresh water and treats should be limited to a small part of their diet.