Eye Spy Bottle. It's a great way to recycle a bottle and entertain your kids for almost no cost - just collect the supplies around your house.
Rainbow Rice Eye Spy Bottle - part of 10 Printable Car Travel Games and Ideas for Kids - Faith Filled Food for Moms
Discovery bottles- Only use Gatorade or G2 bottles for the sensory bottles they are a heavier plastic so they hold up better and keep a unison look so everything looks good.Make sure to ALWAYS seal your bottles securely with hot glue around the top of the lid.
Sensory bottles! They used Voss water bottles. Not sure where to find them but any water bottle will work. use mineral oil for a way to slow down the materials in the bottle. I usually do 2/3 water to 1/3 oil. Can also do just rice and small objects for I-Spy bottles.