I drank exclusively sugar free drinks for a good 15 years and started to notice that my farts started smelling _really_ bad. Like "_I_ need to leave the room" bad. Thought it was gluten or wheat, it wasn't. Changed to sugary drinks for a few weeks -> boom, bowel/intestine issues gone.
Had a second bout of "issues" when Pepsi sneakily changed from pure sugar to sugar/artificial in their non-max lineup. Took me a while to actually read the label and see WTF happened. Now I'm a Coke drinker, not because I like it, but because it's the only one that's sweetened only with sugar.