You could bring a foldable bucket you can get them on SHEIN & Milton tablets x
Collapsible bucket and sterilising tablets, bring your own bottle brush x
You can buy sterilising microwave bags and hotel can do usually microwave it as they usually have them in their restaurants it or book accommodation check it has a microwave.
Same as ceecee said - packed bottle brush, fairy liquid, collapsable basin and sterilising tablets! - just wash in the sink! Could also buy or bring an antibacterial spray if you wanted to clean sink area in hotel room before washing x
Just sterilise with a kettle of hot water