Flaskborste

The curve of this brush head gets into the bottom corners of my insulated tumbler that used to stay stained no matter how much I swished soapy water around. The nylon bristles scrub off dried coffee residue in seconds, and it’s surprisingly comfortable to grip for a quick rinse.

The bristles are packed tight enough that they actually dig into the spiral grooves of my water bottle, which used to stay cloudy no matter how hard I shook it with soap. It’s a simple tool, but it’s genuinely cut my cleaning time in half and the handle gives good grip even when wet. Wish I’d bought

The nylon head is dense enough that I don't have to scrub back and forth a dozen times to get the bottom corners of my water bottle clean. It's become my go-to for anything with a narrow neck, and it hasn't shed a single bristle yet.