I have been making lots of smoothies with spinach and thought I would throw some wilted lettuce from the garden in my lunch smoothie. It. Was. Disgusting. And looks like vomit. I added banana and pineapple and some honey but it was just SO bitter. I choked it down, but its health benefits may be negated by the chocolate I will have to eat to get the taste out of my mouth. 
What is the biggest food disaster you have ever made?