When putting a candle on a cake and then right clicking it will cause the candle to stay on the cake and another candle to fly out. You can keep right clicking or holding down right mouse to dupe the candles. This can happen in both creative mode and survival. Only needs one candle. Video of me doing it in the attachments.
Environment
OS Name Microsoft Windows 10 Home/ Version: 10.0.18363 Build 18363/ System Type: x64-based PC/ Processor: Intel(R) Core(TM) i5-9400F CPU @ 2.90GHz, 2904 Mhz, 6 Core(s), 6 Logical Processor(s)/ GeForce GTX 1660 SUPER/ Minecraft Java Edition/ Snapshot 20w45a
Hey, this is a duplicate of MC-203568.