Sprays can be made water-based (distilled water or cooled boiled water) with possibly a dash of vodka or hamamelis extract or a pinch of salt or a very small amount of liquid soap – depending on what you want to use the spray for. Then the oils emulsify better with the water.

You can also make oil-based sprays with fractionated coconut oil. Other base oils are often too thick and then the spray head clogs up.
For some applications, you can also mix water with a little oil, such as for sprays for hair. Mixing water with neutral hand & body lotion for sprays is also an option!

Sprays with water should always be shaken well before use because the essential oil floats on top of the water.