Instructions
Head left from the Pokemon Tower, exiting Lavender Town to Route 8. Ignore the closed path to Saffron City and continue through Route 8 to battle several trainers. Walk ahead to enter Route 7 and finish battling the remaining trainers.
Approach the two exits at the end of Route 8; take the northern exit to access an underground tunnel. Travel through the path to reach Celadon City.
Walk to the Pokemon Center, turn right and head up the northern path to reach the Game Freak Building. Enter the building and approach the old woman on the first floor to get the Key Item Tea.
Exit the Game Freak Building, retracing your steps back to the Pokemon Center. Head left to exit Celadon City and travel back through Route 7 to Saffron City. Talk to the guard at the entrance of Saffron City by pressing the "A" button to give him the Key Item Tea.