system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some sodas (like Coke) produce a lot of foam when it's poured into a cup, from say, a can, while other sodas (like Sprite) don't produce nearly as much?
gpt
the most important factor in how "foamy" a soda acts is which of its ingredients raise or lower surface tension. Aspartame promotes the formation and persistence of bubbles, as do certain preservatives.

The combination of multiple foam-promoting ingredients and circumstance is why Diet Coke reacts so energetically with Mentos candy.