Spray bottles are an essential tool for any indoor gardener. It's a good idea to have one or two of them in your toolset. They're really useful for:
They've got a property that is very useful among water dispensers -- they spray a fine mist onto the plants. This has a number of benefits:
Looking for an insecticide to use in your bottle? I have two natural insecticide recipes for you to try.
Most good spray cans have a knob you can turn to adjust how fine the mist should be and how targeted the spray should be.
If you have a number of similar looking bottles, make sure you label them. You don't want to mix up your pesticide with fertilizer! A permanent marker is perfect for this and better than paper labels which are likely to wear off (or their text will fade) as they are exposed to water.
Sprays are not ideal as the main method of watering plants. Rather use a watering can, otherwise you'll be spraying for a long time and may wear out the mechanism sooner than later! When I first started out gardening, I tried watering my herbs with one and their growth was too stunted because I was under-watering them.