The honest problem with no-equipment games
Almost every list of games you can play with nothing is a list of games that are fun for about eight minutes: twenty questions, the alphabet game, would you rather. They're fine. They also all decay the same way — once the group has found the optimal strategy, or has run out of genuinely interesting prompts, the game is over even though you're still playing it.
What makes a no-equipment game last is a source of fresh, unpredictable information that isn't coming from the players' imaginations. Human beings are bad at generating novelty on demand, and that's what runs out first.
What genuinely holds up
- Games with a hidden variable — something the group has to work out rather than invent.
- Games where the fun comes from other people's reactions, which never run out.
- Games with a natural end point each round, so the group re-commits rather than drifting.
- Games that scale down to three and up to a dozen without changing rules.
If you have phones but nothing else
This is the common case — no cards, no board, no pen, but everyone has a phone. That's enough for a full hidden-information game, because the only thing you actually need equipment for is dealing secrets privately.
One person opens a browser, creates a room, and reads out five letters. Everyone else joins. From that point on the phones do nothing except hold each player's secret, and the game itself is entirely spoken. No installs, no accounts, no setup beyond the code.
If you genuinely have nothing
No phones either? The classic fallback is to have one person sit out as a narrator: they think of a location, whisper it to everyone except one player, and run the round manually. It's the same game with a human dealing the cards, and it costs you one player.
It's worse — the narrator doesn't get to play, and they know the answer so they can't join the discussion. But it works with nothing but voices, which is sometimes the whole requirement.