I want to say a sentence such as:
They discount so much I can't help but buy!
I went as far as 这家商店打折那么多， but need help with finding a Chinese expression that has the same impression as "can't help but..." in English.
Also, how do you say unlike in Mandarin?
Unlike the Chinese, the British add sugar to their tea.
不像中国人， 英国人把糖放进茶里 （or 英国人在茶里加糖）
I came up with the above sentence and added some variety for the sake of it. Would also like some help on this.
"can't help but" is normally interpreted as： 禁不住就，忍不住就；
"They discount so much I can't help but buy!"
A direct translation is: 他们打了好多折扣，我忍不住就买了/我没忍住就买了. More Chinese way: 他们的折扣力度太大了， 我没忍住就买了。
Unlike: 不像； 和... 不一样；和... 不同;
"Unlike the Chinese, the British add sugar to their tea."
One possible translation is: 和中国人不同, 英国人往茶里放糖. More Chinese way can be: 英国人和中国人不一样， 他们（习惯于）往茶里面放糖.
"They discount so much I can't help but buy!"
Direct translation : “他们打了那么多折，我不买不行呀！”
But for the part "I can't help but buy!" can translate into many option, i just pick out one that i think is the suitable ones.
small info : the discount compare to china is a different phrase. If is 25% discount in mandarin we would say 七五折, which is 75% of the original price.
For Unlike, 不像 i think is acceptable.
A more colloquial translation:
这家店打折那么多，我不买都不好意思(I even feel bad not buying anything)。
这家店打折这么多，我忍不住就要买买买。
This shop discounts so much, I cannot help [but to] go buy buy buy!
can't help 在词典里的翻译通常是“情不自禁”，不过这里如果用“情不自禁”显得有点书面语。通常聊天，直接用“忍不住”就行。
[For] can't help in the dictionary, the translation is normally 情不自禁, but here if [we] use 情不自禁 it seems a bit [like] written language. [For] normal discussions, directly using 忍不住 is fine.
与中国人不同，英国人往茶里加糖。
Unlike Chinese people, English people add sugar to their tea.
"I can't help but buy = 我非买不可"
I thought this phrase is self-explanatory. Perhaps not and seems not that commonly used though it is a legitimate expression.
I even asked my daughter who had 12 years of full time formal Chinese language studies in a Chinese speaking environment whether she has heard it before, and replied "no, but I know what it means"
In any case, the questioner asked for a Chinese expression that has the same impression as "can't help but..." So I suggested the above phrase which I don't consider "advanced" or difficult, maybe a bit classical sounding, but that's about all, and therefore let it stood on its own in answering the question.
So, what is the phrase all about?
Just as in English, often times a double negative phrase has greater communicative impact than a positive assertion, like "I can't get no satisfaction", (from the song "Satisfaction"), "I hardly have no money", and the all time favorite, "You ain't seen nothing yet"
我非买不可 is a Chinese equivalent of a double negative.
我 = I, 非 = not, 买 = buy, 不 = not, 可 = can.
So literally, "I not buy not can"
Or, sensibly, "I cannot not buy"
Hope that helps.
BTW, you can use this handy phrase in all sorts of situations, even in everyday social conversations to sound "elegantly refine"
Just substitute the 3rd verb with whatever activity you have in mind, like, 我非吃不可，etc.
Consider:
which literally translates to something like:
It'd be a waste to not buy it.
I can't help but buy = 我非买不可
