Erm...what? I don't understand. Calorie-per-dollar ratio = p/q for p calories and q dollars. What model are you using where p or q but not both is negative for the apples example but not the BigMac one?
Celery is the classical example of this.
The thing is, the digestion calories are one small portion of the dietary effects of any food.
For example, some increase thermogenesis, so you could account for that
Yes, apart from cold water it seems hard to think any food can provide no calories. Evolution took care of our digestive tract extracting the most of food (unless you're eating paper)