Bottle top waterers are a useful gadget that fits onto a regular plastic drink bottle, use to water indoor plants, seedlings or those smaller watering jobs.
They come with 3 different colours (red, green and yellow) as the tops, so can be used to distinguish what's in each bottle, if you wish to use different solutions, like a feed for tomatoes.
Also a terrific product for the little people who like to help around the garden, allowing them to water but not apply too much water!