Can a Chihuahua eat peaches?
The flesh, yes. The pit, NEVER.
How much: 1 small piece of ripe flesh with no skin or pit, once a week at most.
Why
The flesh provides fiber and vitamins. The pit releases cyanide and can cause an intestinal blockage, which is extremely serious in Chihuahuas.
Peaches in a Chihuahua's diet
Keep in mind how tiny the portions are for this breed: an adult Chihuahua eats roughly 1 to 2.3 ounces (25-65 g) of food a day depending on his weight, and treats shouldn't go over 10% of his daily calories. That's only a small fraction of an ounce. What looks like "a little bite" to us can be half a meal for him.
This information is for general guidance and is not a substitute for advice from a licensed veterinarian. Every Chihuahua can react differently; if in doubt, always check with a professional.