chemical formula: H2CO3

Good or bad: Many people believe that carbonated beverages are bad for bones because of their high acid content. However, research suggests the carbonation isn't to blame. Carbonated water appeared to have no effect on bone health. But one of the biggest concerns about sparkling water is its effect on teeth since your enamel is directly exposed to acid. So Carbonated water is a little bad for our body.
Why add it in Pepsi:
It is the most important part of Pepsi and without this, Pepsi will not have the taste

chemical formula: C14H18N2O5

Good or bad: Aspartame is a bad thing, it have lots of side effect, like: Phenylketonuria, Tardive dyskinesia, but it can effects on diabetes and weight loss, according to a 2014 PLoS One study, rats that were fed aspartame had lower body masses overall. One caveat to the results was that these same rats also had more gut bacteria as well as increased blood sugar. This increase in blood glucose was also linked to insulin resistance. So on the whole, Aspartame is a bad thing.
Why add it in Pepsi:
Some of the consumer unacceptable the sucralose, so the company add this.

chemical formula: C8H10N4O2

Good or bad: First Caffeine may improve mood and Brain Function, boost metabolism and speed up weight loss, enhance exercise performance and protection against heart disease and type 2 diabetes, so Caffeine is a good thing.
Why add it in Pepsi:
Make it addictive and make kids drink more of it, and Caffeine is addictive.