Some of the cheapest science fair projects for middle school (and other grades) come in the form of a questionnaire. Such as taking an opinion poll about a subject. I have seen projects that looked in to personality or physical traits of individuals to see if they were the same as their parents and grandparents.
Best of luck to you and your daughter. Bravo to her for wanting to participate in a science fair program!
First of all, I assure you that you're not the first parent with the 'non-creativity' or money problem! Here are some good ideas:
• Does the shape of ice affect melting time?
• Does covering the mouth really help prevent the spread of germs?
• Which toilet tissue is most biodegradable?
• How does salt affect the boiling point of water?
• Which citrus fruit has the most Vitamin C?
• Does water go through the membrane of an egg?
• Which surface prevents skids?
• Are two ears better than one?
• Which brand cereal stays crunchy longest?
• Which type of insulation works best?
• How do different hair products affect the strength of hair?
• Does the type of soil affect its water carrying capacity?
We've done all of these projects. They are inexpensive and are true experiments.
Talk to the teacher first about the requirements for the project. You can always Google "Science Fair Project Ideas" as well. Also, when you determine what you will need, you can post a request on your local "freecycle.com" (or similar site). You may be able to get all the materials you need for free -- just make sure you arrange a safe pick-up in a public place!