I have never used food tubes. In fact, I have never heard of them. But I definitely had had experience with dogs that are too rough with a treat in the hand. How I have managed that is to hold a treat in a closed fist and offer the fist to the dog. When they try to bite, etc., and get too rough, you firmly tell them, "Off!" (Obviously, that's just the command we use; you could use whatever.) They will keep trying to get it, and you keep telling them, "Off!" every time they make contact with your hand. When they stop touching your hand and trying to get the treat, you reward them with the treat and LOTS of praise. It has worked for all of my dogs.