Ick
The whey protein shakes have that issue for me, too. It's like mega milk-breath funk.
I found the soy ones (EAS Carb Control) were better about it, but, yes, peppermint tea and sugarfree gum kept me going.
Hang in there! I found the pre-op liquid diet pretty difficult to endure and had to remind myself, every day, that it was only for a little while.