A structured pouch that holds its shape rather than collapsing when it empties, intended for people doing longer sessions than a walk around the block.
Single black option with a belt loop and an internal divider, sized for a full session's worth of food.
Who needs a bigger pouch
Anyone running formal obedience or agility work, where you might get through a couple of hundred rewards in an hour and cannot keep going back to a bag. The divider lets you carry two grades of food, ordinary kibble for easy repetitions and something better for the difficult ones.
Using two tiers of reward
Paying the same for everything flattens the dog's motivation. Keep the good food for the repetitions that were genuinely hard, the first recall away from another dog, the first loose-leash pass of something interesting. Ordinary food for ordinary work. The dog learns very quickly which situations pay properly.
Structured pouches are bulkier than soft ones. If you mostly train on walks, the drawstring or waxed canvas pouches are the better choice.