I'm all about reusable water bottles, but you really have to stay on top of keeping all those nooks and crannies clean unless you want to be drinking from a gross lab experiment every day. These cleaning brushes make that an easy task, combining three kinds of brushes into one handy unit:

1. U-shaped silicone brush for removing stubborn stains around the rims of bottles and cups.
2. Stranded wire slit brush for getting down into that narrow groove in a bottle lid where the silicone sealing ring lives, along with the valve where you insert a straw if your bottle lid has one.
3. Stiff corner brush for removing grime and buildup from corner grooves and more.

Those latter two brushes are connected to a swivel point that allows you to swap them around as needed. It also acts as a hanging hole for easily storing the tool on a hook when you're not using it.

Get a set of three brushes for $13 on Amazon, or a set of six for $20.