Placebo Enhancer (5e Equipment)
From D&D Wiki
This watery potion tastes sweet and comes in a variety of appealing colors. A spell or other effect that can sense the presence of magic, such as detect magic, reveals an extremely faint aura of transmutation, though that's most likely just leftover from the potion bottle.
When a Placebo Enhancer potion is sold, the seller may choose any of the following effects to occur to the drinker once the potion is drunk:
The seller must then make a Charisma (Deception) check versus the drinker's Wisdom (Insight) check or Intelligence (Investigation) check. If the seller succeeds, they tell of how potent the potion is, and how its magic is without a doubt very strong. If the drinker succeeds, then they know that the seller isn't being truthful, and is immune to the effects of that potion.
If this potion is drunk experimentally (and the drinker has no inkling of what might happen) then nothing happens.
Creating a batch of 1d6+4 Placebo Enhancers requires 5 gold pieces worth of materials (water, dye, sugar, etc.) and 1 minute mixing it in a container that has held a potion previously. Anyone who sees the making of a Placebo Enhancer is immune to the effects of that batch.