How much alcohol for a 15 year old?

I must have read the op wrong, I missed the part where she says ‘they have to take alcohol because I firmly believe my kids absolutely cannot have any fun or a good time without alcohol’. Could you point it out to me?
far more likely she doesn’t think that at all but is being pressured by her child.

Ignore all the very naive 'none' people. If there's booze there and she wants some, she'll be having some.

Also, ignore everyone else. There's no right answer here.

Are the parents there going to be keeping an eye on things, or disappearing upstairs and turning a blind eye?

Is your daughter sensible enough to drink only what you send her with? Is she mature enough to understand that you're essentially giving her the freedom of an adult, and that she'll be expected to behave like an adult as a result, and deal with adult consequences if she doesn't? Are you willing to enforce those rules/consequences?

Is she used to drinking alcohol? Does she know her limits?

I grew up in a European country where you could legally drink beer/wine in bars/buy it from supermarkets age 16. My parents were fine with me having a few beers/Smirnoff Ice or whatever with friends from 15. We could blag bars/shops at that age with a bit of makeup/fancy clothes, so there wasn't much they could do about it anyway.

We worked on a trust system: If I had a couple of drinks and came home at a reasonable time in a reasonable state, they were happy to treat me like a young adult. If I came home drunk or late or didn't answer my phone, the consequence was being treated like a child.

Is supplying alcohol to minors not an offence in the UK (where I am assuming you live)? I am in Australia and no parent I know would risk openly allowing children that age to bring alcohol to a party where they were in attendance as they would be deemed liable for supplying. They might turn a blind eye but one complaint from any parent and you risk the police showing up. When mine were that age my job required a Working with Children and an Advanced Police Check so my kids knew very well that they needed to make sure their friends stuck to the rules at our place. Mine were all one of the oldest in their years so we didn’t do 18th parties at home so as not to have to monitor who was old enough to drink.

Around that age my mum always said to me if you want to drink with your friends, thats fine, but you do it at home. If you want to try a cigarette, fine, but you do it at home where im safe.
Ive never smoked. Im now 32 and only drink on special occasions. Never got drunk in parks etc as others my age seemed to have. Her being more relaxed took the fun out of it 🤣

Her getting access to alcohol at a party is a different question to "how much alcohol will you supply to your under-age child?".

So my answer is- none. Buying a child alcohol is completely irresponsible, and very illegal where i live. Is it not illegal where you are?

I have never ever bought my under-age kids alcohol. They were horrified at first, but quickly got over it. Did they drink under-age? Yes. But it wasn't from me. I am not going to be the one killing their brain cells thanks.

Oh I remember being 15 in 2007 and my dad would buy me a little 4-pack of blue WKD if I was going to a house party 😅 I would always be dropped off and picked up though!

I definitely won’t be doing that when my children are older, things are just a bit different nowadays. My teenage nieces and nephews don’t seem to be into drinking anyway so I think there’s a cultural shift.

Drinking at just turned 15 is also illegal. What the parents are doing is equally illegal. If I knew this was happening, I’d probably report it.

None

Absolute zero

Assuming you're serious.. a bottle of vodka, 6 pack of beer and litre of cider 😏
Honestly, if you have to ask this question maybe have a good think about your parenting skills

Has she asked for something specific to take? I'd start from there and see if it seems reasonable to you. Perhaps suggest she take some non-alcoholic drinks and a few low-alcohol ones if she wants them? Since it sounds like this is her first party of this type, even if she's allowed alcohol at home, I'd have a talk with her about pacing herself, resisting pressure, keeping track of how she's feeling (e.g., the effects of drinking may not hit all at once and it's easy to drink too much without realising), not accepting open containers, etc.

I am on my 5th teen and it would be zero.

At 15 I had got bored of staying local and was travelling to other cities to go clubbing and drinking like an adult.

My son is far more sensible than I was.

At that age I’d have bought him a 4 pack of fruity cider to take and he’d come home with a couple in his backpack if he hadn’t shared them.

He’s almost 17 now and goes out drinking with his mates at the pubs that will serve him. He’s been extremely drunk once. Now he switches to soft drinks and tends to come home sober or sober-adjacent.

The kids are alright. My generation - Gen X - was/is out of control.

We had a similar situation last year , with my dd still being 15, going to a friends 16th. We knew the parents well, the friendship group was lovely and my dd is very sensible. When she said the parents had agreed to some alcohol being brought, we agreed on 2 ciders.
Dd had a great evening, drank 1 1/2 cans as she was concerned she’d get drunk.
Not all kids drank actually - there’s quite a group of teens who are not interested in alcohol in the slightest (from my dcs friends) so I don’t think ‘all’ teens will secretly drink if parents don’t allow it

None - because she doesn’t want it. Thank god. I did something right

Also I think whilst we were young and did stupid shit, attitudes have changed towards alcohol since.

And I personally wouldn’t send my kid to anyone’s house actively encouraging it at that age.

Does that only work with alcohol?

Just wondering why alcohol is the one mythical thing you absolutely can't forbid as it will make a teenager want it more.

Not class A drugs, beastiality or necrophilia.

Fucking hell. Yes ‘kids’ do drink at 15/16 but for a parent to actively encourage it ‘yeah we don’t mind if you bring your own alcohol’
I would be saying no you’re not going tbh. The parents sound unsafe.

Zero

Lol at all the people saying none. Most teens at some point drink underage. It's far better to try and teach a healthy attitude towards alcohol and know it what they're having, than risk them going crazy and getting someone older to buy them a whole bottle of vodka.

I'd personally get them a couple of VKs or two weak ciders 🤷

Idk what childhood y'all were living on this thread, but I vividly remember girls bringing vodka disguised as water on school trips, and people drinking frosty jacks in fields. Teens have been drinking underage since the dawn of time.

There is a difference between encouraging it Vs letting your child and their friend have can of cider whilst supervised in the house.

The other issue is you can buy her alcohol and then she drinks that as well as the other alcohol that will be there and has more than you'd want her to have. You can't control this either way. I think this is where parents can inadvertently end up putting other parents in shitty positions rather than looking at the ages and demographic of who's actually going to be at the party they're hosting.