I wanna pass my glucose test! NEED ADVISE whoever pass that!

Hi mummies, when do you think it’s a good time for me to start my no carbs and sugar free water and tea diet? My check up for GB is on this coming 27th March! I wanna pass my glucose test!? Please advise when can I start! Should I start now? My only weakness is sugar drinks only? Will it be too late to start now when the date is in few days time?