Tartine Script  Suggested by donshottype 
Dragon ExtraBold Italic  Suggested by donshottype 

AFAIK the Splenda logo was not made into a font.
The _S_ is almost identical to Tartine Script

Dragon TS ExtraBold Italic has a similar weight and tiny serifs like _plenda_ but the tiny serifs are not all in the right places and some of the stroke terminals need to be rounded to mirror the tiny serifs.
Might be something closer but I did not find it in a short search.