We only used ours a few times. And I think all we tried in there was bananas. Although you can use any fruit that gets soft, or grapes without skins ..
I hated how gross and what a PITA it was to clean them .. so I just started giving Hudson bigger chunks and watching him, he was pretty good at chewing right away.
They are great for teething, ice cubes and frozen bananas worked wonders for DS. He also likes to chew on different fruits, mango, apple, cantaloupe, etc.
Jen - Mom to Jillian (10/2008) and Hayden (4/2010)