When I was playing MC I just wanted to explore the area a bit in the creative mode when suddenly the loading strip and the with appear without me ever summoning it from soul sand in this world. Maybe it has something to do with the fact that I drank a strange soup beforehand, but can that explain jm?
There's no soup that Wither conjures up in normal Minecraft.
Maybe you conjured a wither with the / summon command? There are no other options besides the classic route.
If you play with other people, someone may have used the command to do so, or they may have built one themselves.
The command is:
/ summon [creature name]
It can be:
Bow,
it was somebody else
you accidentally entered the command: / summon wither
it has nothing to do with the soup. It only gives you effects.
You are using any mod where the Wither just spawns.