The cake quest in Bridge Duels appears to be an event quest tied to the game’s current or past event content, and the most relevant public hint I found is a Bridge Duels video showing a player “got the cake” during the event, plus a Bridge Duel wiki page for cosmetics and a separate official- looking start page for Cake Duel, which may not be the same thing.

What I could verify

  • A Bridge Duels video from May 2024 shows event gameplay and mentions “we got the cake,” suggesting the quest is likely completed by playing the event objective rather than doing a hidden puzzle.
  • The Bridge Duel wiki result I found is about cosmetics, not the cake quest steps, so it does not confirm the quest path.
  • A “Cake Duel” rules page exists for a different game, so it should not be mixed up with Bridge Duels.

Most likely way to do it

  1. Join the Bridge Duels event mode or queue.
  1. Play normally until your team reaches the cake objective shown in the event.
  1. Push forward, defend your path, and score or collect the cake when the objective opens up.
  1. If the quest is a progress task, repeat the event rounds until the cake requirement is completed.

Practical tips

  • Focus on winning the bridge fight first, because the cake objective seems to appear during active event play.
  • Stay near teammates if the mode is team-based, since the cake objective likely depends on map control.
  • If you are stuck, the quest may simply require playing the event round enough times rather than a special interaction.

Important note

I couldn’t confirm a full step-by-step walkthrough from the available public result, so the exact quest trigger may differ by update or event version.

TL;DR: Queue the Bridge Duels event, push through the match, and complete the cake objective when it appears; the public evidence points to an event- play objective, not a separate hidden puzzle.