Last unit I challenged my students to make a sphere using only 2D shapes. The spheres never worked out well because they kept collapsing in on themselves. For one group, I suggested using toothpicks instead.
They got this far and I gave it to one student to take home and complete.
That gave me an idea for geometry. I gave the students toothpicks and told them to make shapes. After they completed 2D shapes, I asked if they could turn it into a 3D shape.
I asked them to make a model of their work that included the name of the shape and the shapes that it is made of.
When it came time for snack, they opted to keep working instead of taking a break.