I used to soak them, and I’d give them a scrub with a bottle brush then leave for a bit then it’d be scrubbed again with hot water and antibacterial washing up liquid x
Nuk bottle cleaner liquid works for me
Our water is super hot so I usually empty any left over milk, put some hot water in and give them a shake Then I empty the water add a small amount of fairy washing up liquid and add a small amount of hot water, use the bottle brush to give it a good clean and rinse really well and works for me
we use milton bottle wash which has seemed to work wonders x
i rinse the bottles out and then wash them with a bottle brush hot water and fairy antibacterial liquid x