Here's my latest favorite for a "full" feeling.
I buy a refrigerated cookie dough roll at the grocery store. I then freeze it for a day or two (I find it to be more solid for easier insertion).
Since they are normally crimped with a metal ring, I then cut one end of the wrapper off (about 3/4" below the end of the dough) by using a knife.
I lube up my anus and shove the roll (cut end first) into my rectum as far as possible. Interestingly, the plastic wrap provides a little insulation so there is not a "freezing cold" sensation as when I have inserted ice cubes, etc.
Leave the roll in your rectum for a few minutes and enjoy the full sensation. After a few minutes, the outside of the cookie dough begins to warm up. I then squeeze the exposed end of the roll while withdrawing the plastic wrapper. When complete, you have a cookie roll up your rectum, providing a neat full feeling. I then remove any cookie dough remaining outside of my anus. I then insert a large butt plug to force the dough farther into my rectum and into the lower colon.
You can leave it there until you feel the need to expel. The sugar in the dough does seem to accelerate the contractions.
I do not clean up inside afterwards, but insert a large tampon or rolled-up Maxipad to plug my butt. The remaining cookie dough inside will cause the production of runny mucous. All is well after my next bowell movement.
Biodegradable, soft and pliable, and really "filling"....and you can certainly eat the cookie dough once you've expelled it!