So as I'm struggling to get enough protein on the clear liquids phase, I remembered an old article in a bodybuilding magazine that mentioned that one can use pasteurized egg whites as a source of protein to mix with other drinks. I just tried 1/4 cup of them with 1/2 cup juice and I can't tell the difference in taste or texture, but I'm getting 7 g of protein with my drink! You should be able to buy a carton at any major grocery store (just confirm they are pasteurized, so you can have them straight out of the carton).

I love the Oikos yogurt. Even before my preop diet. It has a luxuriously creamy texture and not overly sweet.

Another option is Carbmaster Yogurt. It has 12g of protein and 80 calories. I mixed in 1/2 scoop of [ame=http://www.amazon.com/Optimum-Nutrition-Instantized-Protein-2-7-Pound/dp/B000GIUQOG]Amazon.com: 100% Any Whey Protein: Health & Personal Care[/ame] (or you could use any other flavorless protein power) to add another 8.5 grams.