I can't really remember Pepsi's marketing during the '90s growing up. I believe in America they had a "friendly rivalry" with Coca-Cola where each other's adverts show the competitors beverages in tongue-in-cheek disgrace.
But yeah, Pepsiman would be so cool, especially if they made superhero lore around him. Who knows, maybe Pepsiman was once a regular can of Pepsi until a radioactive superhero bit him.
In my country, Coca Cola/Coke is so dominant that they drove out Pepsi to give up to have a market in Indonesia.
Coca Cola's biggest rival isn't Pepsi.
It's "Teh botol" ("bottled tea" in Indonesian) is an Indonesian jasmine tea drink produced by the company Sosro and sold worldwide.
Coca Cola then has to change strategy where they're finally having their own bottled version of jasmine tea drink besides their own soda drinks lineup.

they could've still took Japan's Segata Sanshiro adverts and made them appeal to western audience with change of box art and marketing. It would've certainly be eye-catching at the time.
Eye-catching, may be. But would they boost sales? That's entirely different thing.
You know that while it might look silly right now, those grid background in SEGA Master System were considered stylish and really standing out in the stores compared to other games boxarts.
But that didn't work much in North America, Nintendo's already dominating the market. Being eye-catchy didn't help much.

Pic source:
https://x.com/sincespacies/status/1952014851821523183