Items you can include in your box: 

Dogs:

Chew toys

Balls

Squeaky toys

Treat packets

Snuffle mats

Long lasting chews

Tinned hotdogs (great for training!)

Cats:

Toy mice

Catnip toys

Chaser toys

Treat packets

Catnip

Blankets

Dreamies / treats

Food sachets

Small Animals (Rabbits and Guinea Pigs) 

Small animal treats

Wooden chews

Hidey Houses

Boredom busters