Some magic items, like a Potion of Growth or Oil of Slipperiness, produce the effect of a spell. For example:
When you drink this potion, you gain the "enlarge" effect of the enlarge/reduce spell for 1d4 hours (no concentration required).
When a magic item produces the effect of a spell, can this effect be ended by Dispel Magic in the same manner as the actual spell?
(Note that I'm not asking about items that actually allow the user to cast spells, such as a Wand of Magic Missiles.)
According to Jeremy Crawford (unofficially via twitter)
Dispel magic can be used against a spell effect created by a potion, but a potion can't be robbed of its magic by it.
Also, the accepted answer to the question you link states the same thing.
This means that, though the potion itself cannot be dispelled of its magical properties, someone who drinks these potions can have the spell-effect dispelled. Because these potions give no other effects outside of the spell effects, the entire potion is effectively "dispelled."
However, there is also the Sage Advice Compendium, which uses a little more roundabout logic to get to the same conclusion.
If dispel magic targets the magical effect from bless cast by a cleric, does it remove the effect on all the targets? Dispel magic ends a spell on one target. It doesn’t end the same spell on other targets.
This reading implies that Dispel Magic can target the "effect" of the Bless Spell, and not the spell itself.
Ask yourself these questions about the feature: Is it a magic item? Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description? Is it a spell attack? Does its description say it’s magical?
This is the guideline for using Antimagic Field, however, the important text there is, "Is it a spell? or does it let you create the effect of a spell that's mentioned in its description." And, while Potions aren't Magic Items [they're Adventuring Gear (Potions)], they do duplicate the effect of a spell.
Finally
...is the spell's duration instantaneous? If the answer is yes, there is nothing to dispel or suspend. Here’s why: the effects of an instantaneous spell are brought into being by magic, but the effects aren’t sustained by magic (see PH, 203). The magic flares for a split second and then vanishes...In contrast, a spell like conjure woodland beings has a non-instantaneous duration, which means its creations can be ended by dispel magic and they temporarily disappear within an antimagic field.
The effect of the Enlarge spell is still a Spell's effect, even though it hasn't been cast from the spell.
While the SA Compendium doesn't explicitly answer the question whether Potion effects can be dispelled explicitly, it does imply that they can be because they create the effect of a Spell. The other part of the SA asks about monster abilities which do not duplicate the effects of spells:
Dispel magic has a particular purpose: to break other spells. It has no effect on a vampire’s Charm ability or any other magical effect that isn’t a spell.
The Vampire's Charm Ability does not create the effect of the Charm Person spell, nor does it list such a spell in ists description; it is a non-spell effect which works differently. But the potions explicitly create the effects of the named spell, meaning that, based on the guidelines for dispellability, they can be treated as if they were spells:
Is it a spell? Or does it let you create the effects of a spell that’s mentioned in its description?
The answer hinges on whether or not magical items that use the "gain the "enlarge" effect of [spell]" are considered as having applied the spell.
The 2019 Sage Advice compendium (page 14) states the following:
Can you use dispel magic to dispel a magical effect like a vampire’s Charm ability or a druid’s Wild Shape?
Dispel magic has a particular purpose: to break other spells. It has no effect on a vampire’s Charm ability or any other magical effect that isn’t a spell. It also does nothing to the properties of a magic item. It can, however, end a spell cast from a magic item or from another source. Spells—they’re what dispel magic is about. For example, if you cast dispel magic on a staff of power, the spell fails to disrupt the staff’s magical properties, but if the staff’s wielder casts hold monster from the staff, dispel magic can end that spell if cast on the target of hold monster.
There are abilities and other spells that can end or suspend magical effects that aren’t spells. For example, the greater restoration spell can end a charm effect of any sort on a target (such as a vampire’s Charm or a dryad’s Fey Charm), and a paladin’s Aura of Devotion can prevent or suspend such an effect.
Extrapolating this, it would seem that, unless the actual spell itself is used (ie cast), the effect is not dispellable. However, a DM may house-rule that such effects are still dispellable.
However, the examples used in the Sage Advice Compendium entry deal with abilities that produce an effect but without referencing a spell. That is, the Vampire's Charm ability does NOT say "as though under the effect of the Charm spell" or something similar.
Some spells take this approach. For instance, Potion of Flying reads:
When you drink this potion, you gain a flying speed equal to your walking speed for 1 hour and can hover.
This potion does something very similar to the spell Fly but does not use the "effect" wording (and allows for hovering).
Because it does not say "gains the effect of a Fly spell," or reference the spell in any way, it would be treated like the vampire's charm ability. To wit: it would not be dispellable.
But Potion of Enlarge does reference a spell and says it produces that spell's effect:
you gain the "enlarge" effect of the enlarge/reduce spell
Dispel magic reads:
Choose one creature, object, or magical effect within range.
Potion of Enlarge's description seems specifically tailored to make it susceptible to Dispel magic.
I think it has to use this wording because it could not say "When consumed, it casts [spell] on the imbiber." That sort of wording would allow Counterspell to be used against it and prohibit Barbarians from drinking health potions while raging. That just doesn't seem right, hence the wording that Potion of Enlarge uses.
I think the general rules for using magic items to cast spells applies here, too:
Some magic items allow the user to cast a spell from the item. The spell is cast at the lowest possible spell level, doesn't expend any of the user's spell slots, and requires no components, unless the item's description says otherwise.
While the rule specifically references items that cast a spell, I think it is not at all a stretch to assume that it applies to any magical item that produces an effect of a spell, whether that's from a spell cast or a simple statement that the user benefits from the effect.
So the combination of these rules suggests that if the wording of the magical item states that the beneficiary has "gained an effect of a spell," it is to be treated the same as though the spell itself had been cast and is therefore dispellable by Dispel Magic. The DC for doing this is treated as though the spell were cast/applied at the lowest level.
