More Awesome Than You!

Essence of Cur Tails and Magically Spiced Sugar are opposing items that can be made by an evil or good witch, respectively. I've done extensive searching without finding much about these except that I find more articles when I spell it "Cure Tails".

After a witch makes the item, they have to give it to their "victim". I could find no way to use it directly on a Sim. The Sim that now owns it does not have the option to consume it, though they can be influenced to do it...sometimes. There's the rub. The option doesn't always appear, and I can't figure out what is necessary for it to do so. 

The first time I used cur tails successfully was with an evil warlock with zero niceness who gave it to his son. He then influenced his son to drink it as there was no option for him to consume it himself. The potion worked, but soon wore off. I did it again and used the batbox to make it permanent. Evil witches have a spell that makes a Sim a jerk for awhile and nice witches have a good mood spell, so I felt that the consumables should be permanent. I can't remember how many nice points the son had to start. He was then given a few extra of these potions to pass on to his spawn because I had no plans to make him a witch.

Son grows up and gives one of the potions to his own son. This son has 4 nice points, but he can't be influenced to drink it. I try all of the other family members (most of whom were BFFs), including the warlock who made the potion, but the option to influence him is not there. So I start messing with his personality to find out why the option is missing. Perhaps he needs to be nicer. So I drag his niceness up to various levels, but the option never appears. I messed around with some of the other personality traits, but nothing seemed to work. He is a teen, but his father was a teen when he consumed his. I also gave a potion to a playable neighbor and a teen in that household consumed it.

I haven't played the good witch as much, but the same thing seems to happen with the magically spiced sugar.

So has anyone figured out the rules?

This baffles me; I've tried the sugar a couple of times, they both ate it directly from the inventory (just like they do with the potions) and they instantly get the 10 nice points thing, which lasted for a while, like, half a sim day IIRC.
No issues, so far. They were both warlock, though: one had a native average niceness and the other only 2 or maybe 3 points.

I see no point to the "niceness" potion.  Any sim can be nice without it.  However, if you have a nice sim, and need him/her to fight immediately, "cur tails" is like spinach to Popeye.

This was my experience with the sugar as well.  A Sim gave it to her father, who had zero nice points, and he had the option to drink it on his menu.  Neither father nor daughter were warlock/witch.  Dad got 10 nice points and went around hugging people all day, and then it wore off.  I was sad; had hoped it would be permanent.  He was having trouble getting dates because his reputation was so bad -- he was always fighting on community lots.

As phyllis mentioned, the "temporary niceness" might come in handy if you wanted a sim to befriend someone he'd normally not bother listening to long enough or be willing to accept nice interactions from. I do wonder if it could get a neighbourhood trashcan-kicker to cool it for a while, especially if you don't play the kicker's home lot long enough to let the potion wear off? Other than that, yeah... not the most useful spell ever devised.

Now THAT's a useful potion!
*pounds fist, makes meanface*