Where do you get the iced tea in Pokemon leaf green version?

i believe there is an old lady in the hotel building in celadon city who gives it to you.
when you get the tea give it to the guards who do not allow you to pass through saying that they r thirsty .give it to them .give it to any on of the guards ,then he will tell that "i will share it with other guards "and will allow you to go through and reach other cities directly instead of roaming here and there . hope this helps you