A cup of Legos?
30 blocks?
An empty box?
Use Legos to make a marble run
Use cotton swabs or popsicle sticks to make a maze for an action figure
Use chalk to make a maze for a remote control car, sibling, or parent
Here are some great challenges from teachoutsidethebox.com
Each challenge provides a materials list, resource videos, space for your blueprint, and questions about what you learned. (If you scan the QR codes, you can find the videos for inspiration and learning.)