Can you tell me whether or not you have juice?
As you can see, "whether" is normally connected with "or not".
Because I'm in a pedantic mood, please be aware that if you start a question with "Can you tell me ..." there is a danger that the respondent will simply say "Yes, I can" or "No, I can't" without giving you the answer you were looking for.
Do you have juice?
Please tell me if you have juice.
Student or Learner