I gut load my crickets with Fluker's High-Calcium Cricket Diet and keep a water pillow in my cricket enclosure. For my mealies I take out the bedding that is in the containers and replace it with the Fluker's High-Calcium Cricket Diet and will place a piece of apple or orange in the container as well as peaces of potato and whatever type of lettuce we have.
Oranges, apples, bananas, coconut, potatoes, and/or greens such as kale, collard, dandelion, and romaine lettuce. Don't forget to do a dry gut load too. Dry gut load is easier to manage because it does not expire as fast and can be used alongside a piece of fresh veggie or fruit. Dry gut load may include items such as oatmeal, alfalfa powder, ground up seeds and nuts, etc.