Diet Coke made with Splenda, while not great for you, is much better for you than Diet Coke made with Aspartame. Anything with aspartame is poison for your body.
http://www.holisticmed.com/aspartame/
On the occasions I have something carbonated, I like to take a 0 sodium carbonated water, add a splash of lime, a splash of lemon and a wheylow packet, mix and voila, homemade and healthy sprite/7-up alternative.
http://www.wheylow.com/
Gums...again, you can probably find chewing gums made with splenda instead of aspartame, but I recommend visiting a whole foods/organic foods grocer and looking for SteviaDent (or order online!). While it also contains trace amounts of maltitol, xylitol & glycerin, at least it is made with Stevia and not an artificial sweetener. It also contains no petroleum or artifical ingredients.
Hopefully someone out there has knowledge I don't about gums made without sugar alcohols and can help you find something without even sugar alcohols in it.