that's actually considered an eating disorder. not to mention, it will really screw with your body. The mouth is what tells the body what it's eating. The body will still think it's eating, and act accordingly. The taste of sugar, will cause the same reactions in your body, as actually eating the sugar. Tho, some will also argue, that there is nothing wrong with tricking your body.
Plus, the strongest taste buds are usually in the back. Notice how something tastes a lot better when you swallow, then when you are chewing?
Do you know how I get away with eating what ever I wish? I eat what ever I wish, and get over it.