Just buy some fresh cheap greens (kale, mustard greens, etc.) and chow on them with a banana or some other fruit -- honest, it tastes pretty good in this combination based on experience (have tried this eating kale in combination with peaches, oranges, apples, plums - so all of these are also good candidates if you don't like bananas). No blender needed, the mouth is the blender. Chew until it hurts, then chew again. Kale should be tedious to chew. Kale and mustards are like 79-99 cents a pound, eat up on those.
1/2 cup is seriously a joke though, right? If you're serious about that then just eat like a leaf of romaine and call it a day.