Sync is not here yet, but people do need to hand a collection to someone else, so here is what actually works.
Export, then import.
- Settings › Data → tap the collection → Export CSV or Export JSON
- Send the file however you normally send files, or drop it in shared cloud storage
- They import it: into an existing collection, or as a new one
SweepTag's own exports re-import cleanly, so nothing is lost in the round trip — which also makes this a decent backup habit regardless.
The caveat worth stating plainly: this is a copy, not a sync. Two people editing after the export produces two divergent collections and no merge. Until sync ships, pick one device as the authoritative one and re-export from it.