Many humans enjoy citrus fruits, but do dogs? Eh, most dogs don't actually enjoy citrus fruits and won't partake. But if your dog is the exception to the rule, then sure! You can give them a slice or two of your Sumo orange - I wouldn't share mine, but that's up to you. If you decide to feed citrus fruits to your dog, do keep in mind that fruits contain sugar that can result in weight gain.
Another potential concern would be the effect of the acidity on your pet's stomach. Too much citrus certainly upsets human stomachs, so we should consider that citrus can also cause doggy stomach aches. If you are going to feed a slice of orange to your dog, you can, but be do so with caution and watch for signs of belly upset incluing not eating, or throwing up. If seen, it's probably best to skip sharing your orange with your fuzzy pal.