Diet Coke contains four calories, fourteen milligrams of sodium, 0.5 grams of carbohydrates, and 0.4 grams of protein.
It's not fattening, but it's certainly not filling. It's insubstantial. It's just barely enough to tide you over but it's not enough to keep you satisfied for long. The bubbles can distract you from that, sure, but they don't stay forever. Nothing does.
You may be just as well off swallowing air from all the overall satisfaction that you get from it.
I am as insubstantial as Diet Coke.