Fleet Phospho Soda IS the prep I had. Yuk. It tastes so nasty it's a good thing you have to drink only a couple ounces. The problem I had was that my procedure wasn;t until mid-afternoon and the elimination part had me SO dehydrated I had a splitting headache and they couldn't get an IV started.
Re the taste, the Phospho Soda comes in unflavored as well as flavored -- I got "ginger lemon" I think it was. It wasn't tasty but I didn't have a problem downing it, and then I chased it with a couple of ounces of ginger ale.
Post-script to my own post #89 -- I forgot to mention: Two nights before the procedure at bedtime, I took two tiny Ducolax (sp?) laxative tabs as instructed (provided by the doc's office). That got the elimination process started, then next afternoon, the first Phospho-Soda, and so on ...