What do Humming Birds eat?

I have a Humming Bird living in my backyard. She has a nest, and she had an egg. The egg hatched and now she has 1 or 2 hungry birdies to feed! I felt bad that it had to leave for a while to find food, so I put up a little Humming Bird feeder with that special formula you buy in stores. She ate that pretty quickly, but now it's gone and I have to buy more. Till then, will she eat watery mashed up fruits like strawberries? What can I feed her maybe? Please answer! Thanks.