This is what I personally do.
Sugar free jello. Then I flavor it with Mio 0 calorie drink flavoring.
A 4 cup box of sugar free jello (8 servings) is 80 calories (10 cals/serving). and is about the equiv of 10+ pudding packs in size (easily, probably 15-20 tbh).
Can down the whole thing in one sitting and not feel guilty about it.
I recently discovered the offbrand jello sugar free, which is half, 5 cals/serving, but when mixing it with the Mio, I haven't been able to get i to quite solidify yet. I'll have to experiment with it.
Also helps w/ the keeping full/hydration aspect of it, since my jello bowl is a quarter gallon of water