Infested Potion is not a vanilla Minecraft potion
It cannot be brewed in survival Minecraft
It is only available through commands, creative mode, or mods/datapacks
Use a command to give it to yourself if cheats are enabled
Java Edition example: `/give @p minecraft:potion{Potion:”minecraft:infested”}`
If that command does not work in your version, the potion is not available in that edition/version
Bedrock Edition does not have a standard Infested Potion item
Use custom commands or add-ons if you want a similar effect