For a short term fast I think those things should be fine. If you go longer, you'll likely find that you can no longer stomach them and/or stand the taste. Also, they may set off hunger pangs, as artificial sweetners are known to do.
As I think I mentioned, I drank black coffee for a while on my first long fast--I probably also chewed some sugarless gum/mints. For the best experience, though, I think just simply going to water is the best bet.
Of course, to each his/her own--try it and see what works--make adjustments as neccessary.
47 M 5'8"
May 4, 2010...... 440? lbs. (Start FitDay Size 60 Jeans)
June 19, 2010.... 393 lbs. (First Weigh-in)
June 19, 2011.... 229 lbs. (164 lbs. gone in one year :-)
Current Weight... 185 lbs. (Size 36 Jeans)
Next Goal 169 lbs. (07/04/12)
Ultimate Goal 165 lbs. (12/31/12)
The best exercises for weight loss are Fork Putdowns and Table Pushaways.