Salam alaikum was rahmatullahi was barakatuh,
Can I lend money (and charge no interest) to a person whom I know 100% that he will use it for haram purposes (like, construction of clubs, alcohol shop, etc.)?
Jazak Allah khair! 
May Allah reward us all the highest level of paradise.
Wasalam
May Allah bless you.
No you should not help him to commit a sin if you know for sure.
And Allah knows best!
May Allah bless you too.
What if I am 99% sure and 1% not sure? Does it depend on certain percentages?
A person can either be sure or not sure. I cannot put a measurement or percentage.
If he is sure then he should not help the other person. If he is in doubt then it is best he does not help him either.
And Allah knows best!
Jazak Allah khair for your answer!!!.