Frogs generally only eat insects, with some larger species also eating small rodents, birds, and even snakes. Unfortunately fruits and veggies aren't something they can eat. Worms are usually pretty good food, though. I often feed nightcrawlers to my toads and African Bullfrog. An Adult WTF should be able to handle nightcrawlers, and smaller worms do exist that might make good food. Worms from the wild, like any typical wild insect prey, can carry parasites that are transferred to your frogs. Stores usually only carry nightcrawlers and a smaller species referred to as "Red Wigglers", or "Compost worms". They have a bad taste that some frogs hate. I had a frog that tried to eat one and never tried to eat another worm his whole life.