Warning! The following contains spoilers from the recent Star Wars Resistance episode "Fuel for the Fire." Read at your own risk!
Star Wars Resistance gave a big nod to Solo: A Star Wars Story in "Fuel for the Fire" when it specifically referenced a key substance from the film. The TV show's Kaz was pressured into helping new "friend" Jace Rucklin sneak into Jarek Yeager's quarters, where the seedy character then nicked some "hyper fuel." The appearance of the Solo-tethered hyper fuel is somewhat surprising, and it should have fans wondering why the starship mechanic has any to begin with.
In Solo: A Star Wars Story, the Coaxium hyper fuel plays a big part in the overall origin story. Han attempts to use a vial of it to negotiate his escape at the start of the film, and it's the exact substance that lands his team on the suicide mission that dominates the bulk of the film. Barring a universe-wide inflations, one would reckon the Coaxium fuel is still just as valuable and rare in Star Wars Resistance, especially while tensions mount between Rebel forces and The First Order.
Star Wars Resistance doesn't jump too far into a deep explanation of the Coaxium, but the Disney series does drive home that it's valuable and dangerous. This is shown when Jace Rucklin, voiced by Elijah Wood, puts too much in his vehicle and almost dies when the ship explodes from the energy. It seems reckless to have that supply on a ship full of shady characters, which once again has us questioning why Yeager had it in the first place.
Star Wars Resistance has filled in a few details about Yeager's past. For instance, we know that he was a Rebel Alliance pilot that participated in the Battle of Jakku. We also know he has a wife and son that have only been seen in pictures. That part doesn't necessarily explain how he would get ahold of some hyper fuel, but understanding his position in life does explain the why.
From Yeager's dialogue with Poe Dameron and his aiding of Kaz, it's easy to assume he's still pretty pro-Rebel these days. A few drops of Coaxium in a Rebel ship that stops by the Colossus could be the difference-maker in a future conflict between Rebels and the First Order, which might be why he had it stowed away. It's also pretty valuable, and an investment he could've used to bring in a cash for surplus for something expensive, should the opportunity arise.
It's also possible Jarek Yeager might have that fuel stored specifically for the First Order. Sure, we have no reason to suspect the former Rebel pilot of switching sides in this conflict, but wouldn't it make sense for the First Order's greatest ally on Colossus to take a Rebel spy under his wing? Obviously, there's little evidence to support this wild theory, but one can never be too certain when it comes to the Star Wars franchise and wild twists!
Unfortunately, Star Wars Resistance hasn't seemed too interested yet in the deeper questions behind why Yeager had the rare substance, or how he obtained it. Granted, future episodes could explain all of that, but this may be one of those references that the writers haven't fully fleshed out with a story. Only time will tell if Yeager's secret hyper fuel stash is extremely meaningful to the series, or if it's just a casual Solo: A Star Wars Story reference.