i want an interesting topic to use for my informative speech in my speech...

This is an example,
Say you're a tight end in football, you could inform people on what the purpose of a tight end is or why the tight end is needed.

You could inform people on the health risks of drinking energy drinks.

Inform them on the procedures a doctor does to remove a tumor.
Maybe how tumors grow..?

Hope I helped

100 Good Informative Speech Topics
http://www.speech-topics-help.com/good-informative-speech-topics.html

What are some of your hobbies?
How to grow a good tomato.
How to give a manicure.
How to bleach your hair.
How to match your nail polish to your dress.
How to pick out shoes.
How to build a bird house.
How to wash a car.
How to act suave around boys/girls.