The step up from a fabric pouch. Waxed canvas resists oil from soft treats rather than absorbing it, which is the reason cheap pouches start to smell after a fortnight.
Waxed canvas in grey, khaki, green or black, with a metal carabiner rather than a plastic clip. Wide mouth that stays open while you work.
The wide mouth is the feature
A pouch you have to open with your other hand is a pouch that costs you a second, and a second is long enough for the dog to stop connecting the reward with what they did. This one stays open so you can go in one-handed and mark the moment properly.
Carabiner rather than a belt clip
Clips to a belt loop, a bag strap or the waist belt of a hands-free leash, and does not pop off when you crouch. Plastic belt clips fail eventually and always at the wrong moment.
Wipe out with a damp cloth. Do not machine wash, it strips the wax.
Part of the Leash Pulling Kit and the Recall Kit.