Cut the apple. That's the trick.
For a small bento, cut the apple into wedges and you’ll have plenty of room for everything else. A whole apple is basically a big round ball hogging the whole middle of the box. Wedges are flat and flexible—they slide into gaps around the yogurt cup or along the sides. You lose nothing except the “look” of a whole apple, which nobody cares about at lunch.
If your heart is set on eating it whole, you’re fighting the box. Swap the yogurt cup for a reusable silicone one that takes up half the space, or just accept that you need a bigger box. But honestly, cutting the apple is the fix.
Your lunch is for eating, not photography.
