No, Grapefruit, orange juice, and apple cider do not burn off fat whether they are eaten alone, in between meals, or with a meal.
Citrus juices are slightly acidic in nature but are much less acidic than the hydrochloric acid secreted by your stomach (pH of 1.2). So any food you eat will neutralize the acid in your stomach. Acid foods do not burn off fat nor alter the fact that all excess food eaten is stored as body fat. Some of these fat-burning diets don’t even recommend a lower calorie intake. Instead, the fat burning diets are usually built around one magic food. Avoid following any diet that recommends one magic food that must be eaten with each meal or daily. They don’t work and even if you lose some weight, you will most likely gain that weight back as you can’t follow that fad diet for life.
A more sensible approach to “burning off fat” is a combination of decreasing your total food intake by eating smaller portions and an exercise program tailored to your weight loss goals.