Some ideas to try with Protein shakes ... Mix with SF pudding, Greek yogurt (plain preferred), Kroger carb master yogurt, unsweetened almond milk, SF cool whip, SF syrups (davinci or torani), SF Creamer. Some docs and NUT allow fruit (berries preferred because they are lower in sugar than other fruit) and if they do allow it, you'll need to mix with Water rather than milk. Also adding ice and blending seems to make a world difference!!
I have tried quite a few different Proteins brands and flavors and have found that I like to use unflavored protein so I can mix it up with all the things I mentioned above. Happy experimenting!