Earn a "gold" medal in all three dog walking mini-games.
Cheaply Feed Chop
Normally, you would have to spend credits to obtain food for Chop, but you can use an easy trick to save yourself some currency. Simply buy the very cheapest food/water and let Chop take a single bite, then swipe the bowl away before it empties. That will count as feeding Chop, but your supply of food shouldn't dwindle. Repeat as needed until Chop is satisfied.