Cheerio are mostly air, there are 100 calories in a cup of cheerios, so this would mean 1/8 of a cup would have around 12.5 calories, which is well under 10 percent of a typical Yorkie's daily caloric needs. I'm not sure how many are in 1/8 of a cup, but it’s a lot, I wouldn't use the sweetened ones. They love the plain ones, so no need giving them a sugar tooth. I don't remember the exact ratio of treats/regular food, but I know if you use the 10% rule you are safe, as long as the treat is not unhealthy, meaning super high in fat or sugar.