To throw in a bit of weird when the our D&D5e crew found themselves transported to a small pocket dimension, I used a modified version of the Molds & Slimes of Vilnid adventure. One of the elements of that adventure are little pod-potions that you can harvest from the slime pits, many of which are actually potions of delusion.
But I wanted a bit more… variety.
So I updated the potions list a bit from the original I wrote. Essentially the potions are 50% likely to be potions of delusion, but in addition, there’s a 25% chance that they also have another effect (including for the non-delusional potions).
As they consumed the pods, the potion effects were rolled on the spot. When they had enough time to go through and identify their potions, we rolled them together and I kept a set of notes indicating which potions were actually delusional without indicating anything to the players.
The potion effects included are mostly a mix of potions from the 5e rules and potions based on those in Forged in Magic from Paradigm Concepts.