請勿把m 巾沖入廁所~英文係咩

m 巾英文係 sanitary napkin, sanitary towel, sanitary pad, maxi pad (US) or tampon(US, a brand name but mean the same thing)
廁所英文係 toilet
沖廁英文係 flush
請勿把m 巾沖入廁所~英文
Don't put the sanitary napkin into the toilet.
Don't flush the sanitary napkin.

Hope the below helps you:
Please refrain from disposing sanitary napkins in the toilet
OR
Please do not throw sanitary napkins in the toilet
OR
Please do not dispose sanitary napkins in the toilet/lavatory/washroom
Good luck.

請勿把衛生巾沖入廁所-----Please don't dash into the sanltary towel the lavatory

Please don't wash the sanitary napkin into a toilet

DO NOT throw sanitary towel into toilet.

Please do not the flush the napkins in the toilet.