sfp – What type of fiber optic cable and termination should be used for temporary outdoor connectivity at an event (UPC vs APC)?

If you have a way to keep the fiber protected/safe from feet and other dangers, it should be fine to use a simple pre-made patch cable. Personally, I would order 2 just in case of an issue with the first one.
As for the termination and equipment, you need to make sure everything matches. To keep it simple, use UPC termination, that is by far the most common in most applications outside of permanent service provider networks. Most SFP transceivers will be for UPC terminations and you will be able to tell the APC ones from their green markings (same with APC terminated cables, they have a green connector housing usually).
Single mode (OS2) is fine. Make sure your SFP transceivers are for Single Mode (SM, LR or similar in the model, and 1310 nm wavelength or occasionally 1550 nm). You simply need matching transceivers on each end as long as your equipment will work with them. Some brands of switch will want a matching brand transceiver but there can be configuration options to disable that requirement. If you are using media converters at both ends of the fiber, almost any transceiver of the right type and speed will work as long as they all match.
The media converter will determine the supported speed of the links, and the transceivers need to match (1 gigbit transceiver for a 1 gigabit media converter connected to a 1 gigabit switch port, etc.). LC connectors will be the most common option for SFP transceivers but there are media converters that use SC type connectors for 1 gigabit links (some use GBIC, some have an integrated transceiver).
That should be about it. It’s quite easy to setup. If the link doesn’t come up on your first try, make sure to try ‘rolling the cable’ which means to swap the fiber connectors on one end (RX to TX or vice versa).