You know, since you are not going to drink/eat a "traditional"/mainstream clear liquid diet, you might want to call your doctor and ask them to just use Colyte ( I think that is it) for the prep. Chances are you will be less likely to dehydrate with that.
OR since it is just a couple of days on a clear liquid diet, just use things you normally wouldn't, and afterward, go back to restricting the HFCS. Of course, you would avoid anything you are allergic to, like grapes.
Maybe someone else will have some better suggestions.
"Be kind, for everyone you meet is fighting a hard battle." -Plato