When looking to spend your precious Gold on pet food, you want the most efficient pet food possible. So, we need to find what is the most efficient at each pet rank, since the cost of feeding pets increases with each rank. The most efficient food in a particular ratio is, therefore, the most powerful and expensive since the ratios lower much more slowly.
As we can see, the highest FP items in the 3 ratios are
5x: 
Soft Drink (100/20)
4.36x: 
Chocolate Cream Sandwich Cookie (1111/240)
4.17x: 
Ambrosia (5000/1200)
So let’s look at these for a moment.
Soft Drink:
Ah yes. An absurdly high FP/Gold ratio, and so cheap too! Or is it? People sometimes forget to factor in the cost of feeding.
| Pet Rank | Item cost + Feed Cost | Adjusted Ratio (FP/Total) |
|---|---|---|
| Common | 20 + 5 | 100 / 25 (4x) |
| Uncommon | 20 + 10 | 100 / 30 (3.33x) |
| Rare | 20 + 30 | 100 / 50 (2x) |
| Legendary | 20 + 60 | 100 / 80 (1.25x) |
| Divine | 20 + 150 | 100 / 170 (0.58x) |
The adjusted ratios are, at best, mediocre, and thanks to the increasing cost of feeding pets, it lowers sharply with every level. In other words, this food item is (predictably) the worst one.
Chocolate Cream Sandwich Cookie:
The next candidate for an efficient food item is the only other food item with a better base ratio than Ambrosia. It’s the Oreo! No, not that one. Let’s see where this food item works.
| Pet Rank | Item cost + Feed Cost | Adjusted Ratio (FP/Total) |
|---|---|---|
| Common | 250 + 5 | 1111 / 255 (4.36x) |
| Uncommon | 250 + 10 | 1111 / 260 (4.27x) |
| Rare | 250 + 30 | 1111 / 280 (3.97x) |
| Legendary | 250 + 60 | 1111 / 310 (3.58x) |
| Divine | 250 + 150 | 1111 / 400 (2.78x) |
It maintains its high feed ratio through Common and Uncommon, being stronger than even base-level Ambrosia. It maintains this edge through Rare. It’s still a decent choice up through Legendary if you’re not buying Ambrosia (since the cookie itself is a lot cheaper), though it comes at the cost of a little efficiency compared to Ambrosia. Once you hit Divine, though, it’s too inefficient to bother with.
Ambrosia:
This is the single most powerful legally obtainable (Admin Sword has more) feeding item in the game. With a whopping 5000 feed power and 4.17x base ratio, it is efficient at all levels and maintains efficiency well. It comes with the highest cost of a feed-only item in the game at $10 of gold per item, but at higher ranks like Legendary and Divine, it’s worth it.
| Pet Rank | Item cost + Feed Cost | Adjusted Ratio (FP/Total) |
|---|---|---|
| Common | 1200 + 5 | 5000 / 1205 (4.15x) |
| Uncommon | 1200 + 10 | 5000 / 1210 (4.13x) |
| Rare | 1200 + 30 | 5000 / 1230 (4.07x) |
| Legendary | 1200 + 60 | 5000 / 1260 (3.97x) |
| Divine | 1200 + 150 | 5000 / 1350 (3.71x) |
As you see, cookies are more efficient at Common and Uncommon. It’s also prohibitively expensive for Rare, even though it’s somewhat more efficient than cookies. But, if you’re serious about maxing pets, Ambrosia is seriously recommended. You’ll need the feed power.
So, if you’re paying money to feed pets, use cookies until you finish maxing Rare, then switch to Ambrosia for Legendary or Divine. The other items are simply too inefficient to bother using and CCS Cookies are cheap enough so that you can get them even with $5 of gold at a time.
