
If you're feeding a complete food, you don't need to supplement with fruit and vegetables.
I raw feed, and do believe they can gain good nutrients from vegetables, so blend them and freeze in batches, lifting a portion out as I need to so that it is freshly defrosted. The reason for this is that once you process them in any way, blending or cooking, they start to break down rapidly, and you loose the nutrients you want to try and give them in the first place. I blend a mix of different vegetables, and sometimes fruit, so they get a good range of leafy, root and pulse vegetables, not always the same ones. I don't often give them much fruit, although during the Autumn, they graze from bilberries and blackberries.
There's no reason why you can't give your dog a chunk of carrot, or the occasional ripe tomato (not the leaves though), or other bits of fruit and veg as healthy treats, you will probably see it come out the other end pretty much undigested int his state though. Things to avoid are onions, broccolli, and members of the nightshade family, so potatoes, avocados, and (as mentioned) the green parts of tomatoes, including the unripe fruit.