The use of fruit for cooking seems to go in alphabetical order. When my sims' household ran out of apples, they started using grapes, and then limes for stuff like pancakes. As long as you make sure to have plenty of apples in the fridge, then the fruit-using meals should always use apples.
I think they're using the ingredients 1st in quality order then in the order they're stocked. I had Sims make melon and grape and yes even life fruit pancakes when plenty of apples were in the fridge. And Sims always prefer ingredients that are in their personal inventory.
That's how they do it. I've experimented around. This is what I've determined:
- Use inventory over fridge
- Use higher quality over lower quality
- Use first item of that quality in inventory list (since apples are usually the first fruit grown, they are usually the first fruit in the inventory or fridge, unless you move them or clean them out).
Example:
Inventory order:
Great Flame Fruit
Bad Apple
Perfect Life Fruit
Perfect Watermelon
Sim makes Life Fruit pancakes.
In order to keep the flame fruit bonus on all cooking sims, I make sure they have only a lower-quality flame fruit along with higher quality other fruits. That is if I let them make pancakes at all. Usually I just have them "eat" under the supreme commander.