Can I still use my warrenty if I spilled juice on my laptop?

Or even could I get a discounted price to fix it? I got my lenovo 15" flex ideapad at BestBuy.

Unfortunately, generally not. Warranty covers damage or problems caused due to normal wear and tear and part failure - accidents are not covered by most standard warranties.

That being said, the best way to find out is to call - can't hurt to ask!

Sadly no, your manufacturers warranty wouldn't cover this sort of misuse
HTH
David