Several people have raised a good point. If you use treat pouches or bait bags, it is important to make sure the pouch doesn't become a discriminative stimulus (meaning that the dog only works if he sees the treat pouch because he knows this signals food is present). It can be distracting to some dogs, or, in other cases if the dog must first SEE that the reward is present before he will listen for behaviors that he already knows well, then this is bribery!
You can prevent the pouch from becoming a discriminative stimulus by not always giving the treats from it - sometimes produce treats from your pocket, sometimes already have it in hand, sometimes have the treat on a table and go to get it even though you may still be wearing the pouch. (many people who compete do use bait bags in training whereas in the competition ring no food is allowed) it also helps to keep the pouch toward the back of your body so it is not as visible to your dog or so he can't stare at it and be distracted by it (unless you are working with your back to the dog most of the time....!)
Another way is by not limiting the rewards to just treats (whether coming from the pouch or pocket as the dog can also learn to stare at your pocket too if you always use the same pocket) but also using toys, praise or for everyday life using environmental rewards.
That way the presence of the treat pouch doesn't become associated with training and listening to you, it's just this object that's sometimes there and sometimes not, and sometimes rewards come out of it and sometimes not...so, the pouch itself is irrelevant to the dog as far as listening to you for behaviors he already knows well....and you can still reap the conveniences of having such a pouch on you, for example it's convenient for holding balls and toys - many schutzhund competitors often use these during training though maybe not exactly this style or model of pouch, they seem to favor the bigger apron-like pouches for holding more toys and treats. And you don't get crumbs in your pocket if you are using food... (I don't like to carry moist or slimy or smelly treats - which are what a lot of the high value treats for my dog are- in my pockets)