Puppy's eating poo

What types of dogs?  Certain dogs have a tendency to be coprophagic (stool eaters.)

What food are you feeding?  If you are feeding a poor quality food, oftentimes there are undigested sugars and carbohydrates that are quite tasty to a dog's nose.

DO NOT PUNISH for this behavior.  Manage the situation:  If you know they eat their own stools, then whenever they go out, take them out on lead and clean up as soon as they eliminate.

To help solve this behavior you can:
add some unflavored yogurt with active cultures into the food.
switch to a higher quality food with less sugars and more protein, with better protein sources.
buy additives to make the excrement less appetizing: (S.E.P. is made by Solid Gold and I've heard mixed reviews about it) there are many of these products available.

We have 2 Pointers. They are 10 months old now.
First we always gave them dryfood, with meat (Pedigree). But that made them very hyperactive (and they are already very wild out of themselves so giving them meat also made them even more wild). So now we only give them dryfood mixed with milk. For breakfast and for dinner.
We also have a very big garden, so they are walking freely there most time of the day.

IMO, that's your problem.  You are not feeding a high enough quality food for them to get the nutrition they need from it and they are eating their poop because of the undigested carbs that pass through in it.
 
I have six german shepherds, a working line of dogs who are very active.  I have about 1/2 acre fenced for them.  My dogs don't eat their own stool, but I feed them Innova or Canidae for breakfast, both MEAT based foods, and homecooked or raw MEAT for dinner.  Your pups *might* be hyper because they are still pups, or more likely from too little training, or a combination of both.
 
Particularly with growing pups you HAVE to provide them with proper nutrition to ensure proper growth and development.  It sounds like what you are feeding is mostly carbs and no where near enough protein.
 
If you want to stop the poop eating, the very best method is to know when they are going to need to go, and be there to pick it up.  Dogs have pretty predictable schedules as far as pooping goes and it's not a huge issue to just snatch it up before they can for a month or so until the habit is broken.

The fact that you were giving meat and now you are giving it with milk makes him realize that some feces still smell like it, they have (as we all know) a good sense of smell and they can smell the unprocessed food that is still in the feces, that might be one of the reasons, i give my dog only dry food and never eat her feces
 
Some people say that a reason might be that your pup is bored, since he is hyper he needs more stuff to distract his mind and if he does not have that he might eat the feces out of boredoom
 
I dont want to start a debate about dog's nutrition with anybody so you can choose which advice is better for you, you can try all of them or just a couple

I have switched my two over to a kibble/with raw and cooked meat diet and they have actually not practiced coprophagia for a while.

I'm not sure if it works, but I read a lot of dog magazines. There are some things like Dis-Taste and For-Bid that are suppose to stop them from eating their poop. But also I think [link>http://forum.dog.com/asp/showProfile.asp?memid=6117]glenmar[/link] might be right, maybe they don't have enough nutrition in the food you're giving them.
 
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I saw with my first litter of fosters....they came without momma and Sheba kicked into momma mode and did the poop eating to keep the den clean.  Everyone else decided that was a COOL thing to do.  I had 7 pups and three adults, so TEN poopers and by golly I snatched each and every pile as soon as it hit the ground to break them of the habit.
 
I personally just don't like adding STUFF to their food.  I'd rather just pick up the problem before it gets eaten.  And sometimes you have to be REALLY fast.

You don't say whether the dry food (with meat) was a complete diet.  If so, it would explain hyper behaviour, because they are getting two lots of complete foods.  This can create an imbalance in the diet.  It also means two lots of preservatives and additives rather than one.
 
You do not need to add milk to their food.  Dogs are lactose intolerant. Lactose interrupts the aborption of other nutrients.  In some dogs this manifests itself as diarrhoea.  In yours, it is contributing to the poo-eating problem because the food is coming out even less well digested than had milk not been added, and therefore even more viable for "recycling".  So; a better quality food and stop adding milk.
 
By now it is a learned behaviour and they will need retraining to cure it.  Do not punish them for it, just be quick about cleaning up.  Do as glenmar says for long enough and the habit will disappear.
 
Adding pineapple to the diet is also meant to make it unpalatable to the dog.

Ummmm, I tried pineapple.  Chunks and crushed.  It doesn't digest, they LOVE pineapple and it seems to taste better the second time around.  So for US, it increased the problem.
 
My Mom has a lot of recipes that use crushed pineapple.....needless to say I had trouble eating some of those things for a very long time......