Aloha and mahalo for your review.
Sorry you didn't have enough money to pay for your lunch. Most of the trucks take credit card, so it is surprising to us that you had problems to buy food at any of the ~15 food trucks.
We mention in the description of the tour guests should bring cash for lunch. So, it's a bit odd that you claim you didn't know about it.
Another option could have been for you to call our friendly customer service and ask if you need cash.
Another option could have been you asked the guide to stop at an ATM - there is actually a bank at the food trucks. You could have used it to get cash.
The good news: You survived without lunch, otherwise you would not have been able to write this review ;)
Much ALOHA,
Daniel