Stainless steel bottles get scratched easily, if you want the paint to last long avoid washing the bottle with hot water.
Do not over fill the water bottle, fill it till the bottle neck only.
Do not freeze your water bottle this may cause bouldy base.
Buy a drink bottle pouch or cover to protect the paint of the water bottle. Bottle pouch also works as an insulation agent for keeping your water cold for longer period.
Clean your stainless steel bottle lid weekly, this will stop the mold from growing under the lid.
Wash your water bottle with some warm water to lossen the residue build up and than clean it with a bottle brush.