cheating on pre-op liquid diet
I would also suggest you check to see if you can not use slimfast. There is a lot of carbs and calories without much (relatively speaking) protein. There is a ready to drink shake called Pure Protein that you can buy from costco or sams. It will do a much better job of saitiating you compared to simfast most likely. More protein, less cals, good on vitamins, less carbs The carbs are what can drive you crazy- minimize them if you can. The first 4 or 5 days is the hardest, then it gets easier.
I had a cheat with 5 Guys in my preop liquid diet. The sky didn't fall and I am doing very well overall. What was critical about that cheat is what I learned from it. A poster here pointed out that the hubby was enabling. We had a looong talk about that and this was a HUGE step forward in getting the eating habits cleaned up for both of us. Try to identify what is causing the cheat (and also specifically the food you chose to cheat with) so that you can come up with a plan to not repeat the mistake.
It does get much much easier after surgery, although you will always have to choose the right foods. Hang in there and focus on constant imrpvoement- not perfection.

Surgeon: Chengelis Surgery on 12/19/2011 A little less carb eating compared to my weight loss phase loose sleever here!
1Mo: -21 2Mo: -16 3Mo: -12 4MO - 13 5MO: -11 6MO: -10 7MO: -10.3 8MO: -6 Goal in 8 months 4 days!! 6' 2'' EWL 103% Starting size 28 or 4x (tight) now size 12 or large, shoe size 12 w to 10.5 150+ pounds lost
Join the Instant Pot Pressure Cooker group for recipes and tips! Click here to join!
We all had issues with eating, which is why we all sought surgery. Is it a choice to change the type of shake you are using? That particular one has a lot of carbs, which will trigger cravings. If you are able to, check out Premier Protein (ready to drink) out of Sams or Costco- better nutrition profile, more protein for the calories, and low low carb.
I cheated twice on my preop diet. I made it to goal, so yes... it is possible. But, work your tail off RIGHT NOW to stick to it. Every little thing you do right now will help you to be more succussful after surgery.

Surgeon: Chengelis Surgery on 12/19/2011 A little less carb eating compared to my weight loss phase loose sleever here!
1Mo: -21 2Mo: -16 3Mo: -12 4MO - 13 5MO: -11 6MO: -10 7MO: -10.3 8MO: -6 Goal in 8 months 4 days!! 6' 2'' EWL 103% Starting size 28 or 4x (tight) now size 12 or large, shoe size 12 w to 10.5 150+ pounds lost
Join the Instant Pot Pressure Cooker group for recipes and tips! Click here to join!