Food and consumables for the ISS, or low-cost satellite launch are likely targets.

A kilogram of water on Earth is worth a few pennies. In space, it's worth $5,000 - $10,000. The value-add difference is the launch cost.

Take a bunch of cheap stuff you'd like to have (but don't need essentially, and can readily replace), and pack it on a refurbed booster. If successful, you've gained a few thousand dollars per kg mass. If failed, you're only out the source materials (and the booster, though since this is a test, it's the outcome that's most significant).