Do sponsors ever do one-off event sponsorships instead of full season deals?

Yes, though it's less common. Mike DeFord mentioned sponsoring racer Pete Soren for one-off events like the Baja 1000 or short course races based on specific company needs at the time. These opportunities arise when a sponsor has particular marketing needs for a specific event or when they're using a side marketing agency for clients. The key is that even one-off sponsorships require an established relationship - Pete had worked Mike for years before receiving any support. One-off deals can be valuable for creating PR and attention even if the racer isn't a podium contender.