Bottle caps are the currency in Fallout Shelter. You will get this naturally when going for the 100% since they're used for everything. Caps can be earned by:
- Collecting resources from a production room.
- Rushing a production room successfully.
- Sending a dweller or Mister Handy to explore the wasteland.
- Killing, then looting raiders.
- Selling weapons or outfits.
- Leveling up a dweller (The amount of caps rewarded equates to the dweller's new current level.)
- Levelling up dweller stats at training rooms.
- Completing objectives.
- Receiving them in lunchboxes or in a starter pack, in units of 100, 500 or 3000. Caps from lunchboxes add-up even when 999,999 caps has been reached.
- Finding and selecting the Mysterious Stranger.
- Receive from Bottle & Cappy when they stop and dance.
- Collecting them from the Daily Report.