There's a version of Diet Coke sweetened with Splenda, but Coke Zero is sweetened with aspartame just like regular Diet Coke. The Splenda Diet Coke isn't bad,

There's a version of Diet Coke sweetened with Splenda, but Coke Zero is sweetened with aspartame just like regular Diet Coke. The Splenda Diet Coke isn't bad, but it does taste a little different than normal Diet Coke or Coke Zero. Look for the Diet Coke cans with a yellow label to find the Splenda version.