Please give what you can.
( Please ( ( give ( what ( you can ) ) ) . ) )
(ROOT (S (INTJ (UH Please)) (VP (VB give) (SBAR (WHNP (WP what)) (S (NP (PRP you)) (VP (MD can))))) (. .)))
You don't have to give anything.
( You ( ( ( do n't ) ( have ( to ( give anything ) ) ) ) . ) )
(ROOT (S (NP (PRP You)) (VP (VBP do) (RB n't) (VP (VB have) (S (VP (TO to) (VP (VB give) (NP (NN anything))))))) (. .)))