I couldn’t stand the sickly sweet taste of the shakes either, and there were plenty of people with similar comments when I did the diet a few months back.
For the fish burps, try taking the fish oil capsules with food.
For the shakes: get a tub of decaff instant coffee and use that with the vanilla and chocolate. It’ll kill the sweetness and make it easier to stomach. I used two heaping teaspoons per shake. Experiment to find what amount works for you.
Use pomegranate concentrate with vanilla and strawberry. Make SURE the stuff you order has no sweetener or sugar in it. It’s very tart, and again a little will kill the sweetness in the shakes.
The banana flavor was the only one I never had to mix with anything.
One alternative is to use the Grow! Whey powder, which is unflavored and much easier to digest. But be careful with it; it’s loaded with chlorestorol, while the Metabolic Drive has none.