I would not say either! I would say "you can believe me that the soup is really delicious" or something like that.Why would you use the word "lie"? I am not sure I understand you.

Did you mean you tried a weird-looking soup that tasted bad, and you want to play a joke on your friends by saying it's actually really delicious to get them to try it? I think it depends on how the conversation is going and what sort of person your friend is like. Here's an example conversation that might happen between you and a friend whom you are going to play the trick on, and how you may reply him/her: You: This soup is delicious! Friend: No way! It looks strange... You: It does, but trust me, it's really good! Friend: You're lying... You: Why would I lie about a bowl of soup?! Friend: I don't know... You: Well, it's your loss! Here I am, just trying to recommend you something delicious and there you are calling me a liar... (pretend to be a little hurt by his/her words) Friend: ... Well, okay. I'll trust you. I'll try it. *SUCCESS!* Hahahaha I hope this helps :p But in all seriousness, for your friend's sake, I hope the soup doesn't taste too disgusting! NOTE: the above conversation may be perceived as childish. So if it's not alright to be childish with that friend, or if you think your friend might become offended by it, please do not attempt it!!!