Heat oven to 350 degrees F; grease cookie sheets with cooking spray.
In large bowl, mash the tuna into smaller pieces.
Add flour and milk. Mix well.
Pour in water and oil. Mix well again.
Beat egg in separate dish until dish until egg is foamy texture. Add to mix. Mix well. The dough mix will be sticky.
Using your fingers, shape dough into small bite-size balls, about the size of a marble. Put balls on prepared cookie sheets. Flatten with hand.
Bake for 10 minutes.
Remove treats from oven. Wait five minutes, then turn treats over.
Bake 10 more minutes or until golden brown in color.
Place treats on cookie rack to cool.
Cool for 15 minutes. NEVER give hot treats to your pet.
Store in airtight container and store in refrigerator or cool dry place.