You take the good treats to the park. Your dog spits them out, or does not look at them at all. The same treats work fine in your kitchen.
This is one of the most misread things in adolescence. It looks like fussiness. It is almost always arousal or mild stress.
What refusing food usually means
Eating is a fairly relaxed behaviour. When a dog is excited, worried or scanning hard, appetite tends to switch off. Working below the level at which your dog reacts is the condition for learning near a trigger.
So the food is not the problem, and neither is your dog. The setting is asking for more than they can manage right now.
Check the ordinary explanations first
Weigh breakfast. A dog who has eaten a full bowl an hour before the walk has little reason to work for kibble outside.
Take food they never get at home. Cooked chicken, cheese or hot dog pieces beat a dry treat from the cupboard.
Check the treat is easy to eat. Hard, crumbly biscuits are awkward to take on the move, and many dogs give up on them.
If the refusal is new and also happening indoors, book a veterinary examination before you change any training.
Then change the picture, not the dog
If food still goes untouched, you are too close to whatever is holding your dog's attention. Distance is the dial you have. Quiet is the other one.
Tonight, feed 5 treats in your own doorway or front garden, before the walk starts. If they eat there, that is your working baseline.
Tomorrow, walk to a quiet spot 100 feet off the main path. Sit down and feed 1 treat every time your dog looks back at you.
If they will not eat, move 20 feet further out and try again. Keep moving out until food works, then stay at that distance for a week.
Food refusal is useful information rather than a nuisance. It tells you, in the moment, that you have gone past what your dog can handle today.
What not to do
Do not skip breakfast to make your dog hungrier for a hard environment. A hungry, over-aroused dog is still not eating.
Do not push closer to prove a point. Repeating the too-hard version teaches your dog that the difficult thing keeps arriving.
Do not swap to leash pressure or a stern voice because the food did not land. Reward-based methods are what we work with, and what is recommended for behaviour change.
Safety note
Refusing food outdoors is often ordinary arousal. It is not ordinary when your dog is also trembling, freezing, trying to bolt, or growling. Speak to your veterinarian first, then to a qualified behaviour professional. A dog who stops eating indoors as well needs a veterinary examination.
Today's version, in one line: better food, more distance, and 5 paid look-backs from a spot your dog can already eat in.