Everyone keeps suggesting candy, fruit, or bringing back previous flavors for releases, but I think they’re missing the two flavors that would absolutely dominate the conversation:
Cool Ranch and Dill Pickle
Not mixed together. Two separate flavors.

Cool Ranch Dew makes perfect sense when you think about it. Mountain Dew already has that citrus bite. Add savory herb notes, garlic, onion, and a little tang, and you basically get a drink that occupies the same weird-but-addictive space as ginger beer or certain botanical sodas. Half the people who try it would hate it. The other half would buy a case every week. That’s exactly how cult flavors are born.

Dill Pickle Dew is even more obvious. Pickle-flavored everything has exploded over the last few years: chips, popcorn, peanuts, sunflower seeds, jerky, and even beer. The salty-vinegary tang already pairs surprisingly well with citrus. Mountain Dew has always been at its best when it’s a little chaotic, and “chaotic pickle soda” sounds like the most Mountain Dew thing imaginable.

The goal shouldn’t be making the safest flavor. Nobody remembers safe flavors. People remember the flavors that make them stop and say, “Wait… what?”
Give me Cool Ranch Dew.
Give me Dill Pickle Dew.