OK, I'll say it, it actually IS more complicated to wean a dog off treats than many trainers will lead you to believe!
Now, this isn't an excuse for you to immediately drop all your positive/ motivational training methods and grab the nearest choke chain or shock collar! (Trust me, it's even *harder* to wean a dog off collar jerks or shocks! I've trained with both methods and "My dog only listens if I've got treats" versus "My dog only listens if he's wearing the shock collar" really boils down to the same issue.)
There's no really great way to wean dogs off the shock collar -- you basically just have to keep shocking the dog until you zombify it, or switch over to some other form of punishment for bad behavior, or some trainers will give you the caveat "He's probably NEVER going to be reliable without the collar on" -- but weaning off treats can be done thoughtfully and methodically. Here are some simple exercises to try that can get you and your dog off the treat bag crutch!
Exercise 1: Treats off the body. Set your treat bag down on a counter or table, preferably with the dog watching. It should be clear to the dog that you don't have any treats in your hand -- I will often show my empty hands to the dog! ("Nothing in the hand!") Guide or "Let's go!" your dog away from the treats, then ask for a sit. Did you get it? "Yes!" and trot over to the treats, give one to your dog. Lesson: Just because the dog doesn't see the treats upfront, doesn't mean that he won't still get one.
Exercise 2: Harder work, Higher pay. Try a series of sit or down-stays. A 1-second stay gets praise. A 2-second stay gets praise. A 3-second stay gets the treat. Then try again, starting with a 2-second stay, which gets praise. The 3-second stay now gets praise. And a 4-second stay -- treat! Lesson: The harder the work, the move value for the dog.
Exercise 3: Non-treat rewards. The world is full of things that your dog likes and values, which you can use as a reward! The next time you get ready for a walk, ask your dog to sit (or down, or whatever.) "Good dog!" praise as you leash it up and head out the door, as if leashing and starting the walk was actually the reward for the good sit! (Most dogs, honestly, would rather have a walk than a bit of hot dog anyway.) Lesson: Rewards come in all forms, not just treats.
Struggling with weaning the dog off treats is COMMON. There's no reason whatsoever to give up on training because "He only does it if I've got treats!" Give me a call if you need any help with this; your dog might benefit from more cold trials (I can show you how to do those) or by using a marker word (I can show you how to do that) or by doing some relationship/engagement (non-treat) training (I can show you how to do that too!)