I'm fairly certain that aspartame is a safe alternative to sugar. That being said, I'm going to try and go aspartame-free for the next week -- then returning to it -- and seeing if there are any ill effects.

As a replacement, I'll be switching to sucralose (Splenda). Since the vast majority of diet beverages use aspartame, though, I'm going to be making a lot of my own drinks for this experiment.

Take, for example, iced tea. Here's a simple recipe for it that I found on the web. It tastes great, is really smooth, and since it's just tea and Splenda, has barely any calories.

Ingredients
4 tea bags (I use Earl Grey)
2 litres water
Sugar or sweetener (to taste)
Lemon juice (to taste)

Procedure
1. Unwrap and remove all paper from the tea bags (if necessary). Tie them together and put them into a 2 litre pitcher.
2. Boil 2 cups of cold water. Pour the boiling water into the pitcher and allow the tea to steep for at least 20 minutes.
3. Squeeze out the tea bags into the pitcher, then discard. Fill the pitcher with cold water to the 2 litre level.
4. Add sweetener and lemon juice to taste. Refrigerate, then serve.

I'm going to play around with making iced coffee tomorrow. It'll likely have more calories, though, since most recipes have heavy cream in them.