At least we know his "T" key isn't broken ;P
OP: Some ideas:
1: The truck is a decoy full of mercs or drones. The runners aren't the target - a second group of runners is trying to heist the cargo and the corp is trying to catch them in a trap. Your players' runners are just caught in the middle.
2: Counterfeit foreign money which a corp is using to destabilize a corp in another country. With the exchange rate and fencing costs the loot is still worth quite a bit - but not if the runner burn it and shoot it all trying to stop the truck.
3: Stolen artwork. Fencing this more valuable loot is even harder because the international art markets watch out for this sort of thing, so fencing fees will be higher and there's a significant delay in the payout. Also, damage to the artwork is just as big of an issue.
4: The Italian Job armored car heist: the runners know the container will be coming out of the docks on a truck at 1 AM. They arrive early and set up. At 1 several trucks pull out at once and split up. Which one do you follow? Or do you split up the group and follow them all?
5: The cargo is a shamanic lodge (if your edition of SR still uses those) which prevents astral inspection and trespass. Some other valuable goodies are inside.
6: The inside is wallpapered with a living seaweed net which similarly prevents astral inspection and trespass.
7: Caged monster - possibly sentient and wants to escape - preferably difficult to transport unless they can seize the truck and drive it. Such as: mermaids in a big fish tank, an intelligent octopus augmented to disarm underwater mines, a Little Shop of Horrors plant that needs an enclosed space because it produces a protective cloud of fumes, etc.
8: Illegal reproductions of 20th century sci-fi memorabilia. Exact same problems as artwork above.
9: Cursed idol that remains with you, ruining your life, and can only be removed if someone else steals it.
10. Curse of the Black Pearl: Big stone chest of skull-embossed Aztec gold coins.
11. Little Dizzle: Dozens of captured scientists and lab assistants from some other corp, being transported to interrogation. One of them knows the formula for a valuable product: a cookie that produces an exothermic reaction when you bite into it, meaning every cookie tastes and feels like it's fresh from the oven even if it's been two years since it was baked.
12: A smaller truck driven by a pair of dwarves that drives out of the back going the opposite direction as soon as the rear doors open.
13. Defective pleasure-bots stacked like firewood. They're never in the mood for love and prefer talking about shoes and miniature dogs. Runners hired by an AI Rights policlub to rescue them from the incinerator.
14. The Devil's Forklift, a hulking construction drone with lobster claws that, despite dozens of incidents and code wipes, just keeps killing nearby workers in seemingly-explainable workplace accidents. It's an expensive model, so rather than getting scrapped it gets sold to some other unscrupulous company. Its murder count is now in the low hundreds. When booted up a cheery emoticon appears and it functions normally ... until the right moment arrives.
15. A very fancy sports car - which has been modified to drive very fast and slowly slay the driver. An activist biker policlub designed and built the Murdercar, to swap it out with a certain dilettante's identical model, in retribution for his several hit-and-run killings of random bystanders because he drives too fast. The runners were hired by a rival dilettante because he's envious of the other and wants the same car as him. If the runners steal the car (and the driver survives the experience), they will be pursued by the biker club's attack drones.