Remove the label from the water bottle. Goo Gone will help get rid of any residue that's left.

Fill the bottle half full with baby oil.

Add silver glitter on top of the baby oil (About 1/2 teaspoon of glitter)

Add enough water to a measuring cup to fill the rest of the bottle, then add approximately 8 drops of purple food colouring and 5 drops of blue food colouring. The more food colouring you add, the more opaque your galaxy will be.

Mix the water and pour it into the bottle, leaving about 3/4" of air space in the mouth section of the bottle.

Screw the lid back onto the bottle. You can seal it closed with tape or glue if you like.

Shake the bottle vigorously and watch the glitter move up as it settles!