drink alot of fluids (crystal light) sf popsicles, chicken broth.....the only tip i can offer is not to cheat. you are preparing your body for surgery. you need to be mentally strong to do this liquid diet before. you have a liquid diet after surgery also (and if you cheat on that, you could hurt yourself).
please, do this for you. 11 days is nothing compared to the reward of better health for you after surgery. you can do this, if you want too
all the best and congrats on your upcoming surgery.