Use miniature marshmallows to reinforce non-standard measurement and estimation.
Using miniature marshmallows estimate the length of the toothbrush. Then measure half way of the toothbrush with marshmallows and do a second estimate. Finally, measure the whole toothbrush with marshmallows and give an actual count. Compare the actual count with the estimates and discuss. If you eat any of the marshmallows, make sure to brush your teeth!