What would you feed a 10months old doberman we have tried a lot of different foods.
How can u build them up

What do you mean by building up? Adding muscle, adding weight?

There are a lot of posts here about what people do and should feed their dogs - how much, what products.

Some people feed "natural."

What does your Vet recommend?

I would recommend a high quality puppy chow for a large breed dog. You don't want them to grow too quickly as this will put them at a higher risk for developing joint issues.

There are two members here who are very experienced and knowledgeable with that breed, I am sure they will be around soon; and will be able to provide you with more info.

A doberman should not be 'bulky' at only 10 months of age.
They don't start gaining a lot of muscle until 2 YEARS.

Puppies should always be on the lean side until completely finished growing (and even then it is healthier to keep them lean than fat)
You should be able to easily see the last 2 ribs when the dog is walking/running. Spine and haunch bones should not be visible.

Muscle tone should be visible, but not overly defined at this age... you should just be able to see the muscles move under the skin when the dog moves.

If the dog is too bulky/fat/muscled at such a young age it can cause problems later in life with their joints.