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. They come in different sizes you can find smaller ones for small hands if you need to.
Make sure to ALWAYS seal your bottles securely! I cannot emphasize this enough. Unless you want your bottle opened and the contents poured out. SEAL IT… with glue. Duct tape can be peeled off by a determined kiddo. Glue is much harder for them to open up.
Sink or Float Bottle
Place items that are heavy enough to sink in water, like marbles, in an empty plastic bottle.
Place items in the bottle that will float, like straws that have been cut into little pieces.
Fill the bottle with water. Seal shut with hot glue.
Let children predict what will happen and then shake the bottle vertically, horizontally and upside-down. Children should be able to see which items float to the surface and which items sink.
The Fish Tank Discovery Bottle
When I was teaching this was one of the most popular science bottles. All of us used to make this one because it was fast, easy, cute, and cheap if not free to make! All you need is some water balloons, water, and fish tank gravel or small rocks.
For a list of ALL my amazing DISCOVERY BOTTLE IDEAS click the link or the image below
Below Squinkies and plastic water gems