Dextrose plus bloating is a pretty common experience. Dextrose is a water binder. It binds water in the stomach, so it stays there longer, and can take water from the intestines and blood. This leads to that bloating and even cramping and diarhea for some people.

I don't know why Cell-Tech recommends an additional glass of water. Maybe it's to provide water so its not robbed from the intestines.

But I agree with Sleazy that it seems like all that water will only enhance the bloating. Many people just can't handle all that dextrose, though.