Advance warning: there are very few chocolate frogs in what follows. Disclaimer: I will be saying a lot about how I think almost everyone feels about present-giving; I am describing, not endorsing.

I think your idea of what birthday present giving is for differs from that of the rest of society (including your sister). I think

• you think that when A gives B a present, the point is to benefit B, and A will (subject to limitations of budget, time available, etc.) want to give a present that benefits B as much as possible;
• practically everyone else would say something like that if asked, but actually behave as if the point is to enable A to demonstrate that they care about B and understand B's tastes well enough to buy something B likes. (So A can feel good about being caring and insightful, and B can feel good about being cared for and understood.)

From the first of those viewpoints, giving money makes a lot of sense. But from the second, it makes no sense at all. Therefore, giving money for a birthday present is unthinkable for most people -- and if you ask to be given money, you will almost-literally not be heard; all that will come across is a general impression of complaininess and unreasonableness.

I think you also differ from the rest of society (including your sister) about what's an appropriate reaction when you get something you don't like:

• you think you should say "oh, no, I didn't want that; please don't do that again" and make a suggestion of something better for next time;
• practically everyone else thinks you should pretend you really like it and act just as grateful as if you'd been given something perfect.

This is mostly a consequence of the other difference. If the point of giving a present is to demonstrate your own caring and understanding, then having it rejected ruins everything; if it's to give something genuinely beneficial, the failure is in the poor choice of present and the rejection is just giving useful information.

And now remember that "please give me money" is unthinkable and therefore can't be heard; so "I don't like X; please give me money in future" will be heard as "I don't like X, and I'm not going to suggest a better alternative for next time", and since you haven't (from the giver's perspective) actually made an actionable suggestion, it's quite possible that they won't remember that you specifically didn't like X; just that they gave you something and you were unhelpfully complainy in response.

So now here's how I think your sister probably sees it. (I'm going to assume you're male; let me know if that's wrong and I'll fix my language.)

"My brother refuses to say what he wants for his birthday. So, with no information to go on, I got him some clothes. After all, everyone wears clothes. And then, when he gets them, instead of being grateful or at least pretending to be grateful, he flies off the handle and complains about how he hates getting clothes!"

Whereas, of course, from your perspective it's

"My sister keeps getting me clothes for my birthday. I've said more than once before that I want money, not clothes, but she just doesn't listen. And then she gets upset when I tell her I don't want what she's given me!"

OK, so how to move forward? In an ideal world, part of the answer would be for your sister to accept your preference for being given money. But let's assume that's not going to happen. If you can cope with accepting blame for things that aren't altogether your fault, I think the most positive thing would be to find some things you would be glad to be bought, make an Amazon wishlist or something out of them, and say something like this to your sister:

I'm sorry I got cross with you about my birthday present. I shouldn't have, and I do appreciate that you were trying to give me something nice. [If you actually did like any of the clothes, this is where you can be more specifically grateful.] But, really, being given clothes is difficult for me because it usually turns out that at least half of what I'm given doesn't fit or doesn't go with other things in my wardrobe or just isn't what I want to wear. I never really know what to ask for, which is why I've just asked for money before, but I've tried hard to come up with a list and you can find it by searching for my name on Amazon. I'm sorry to be so difficult to buy for.