It used to be that you could visit the sky bridge of the Twin Towers for free, but that is no longer the case.
They've retooled the visit and for 80 MYR you can stop at the sky bridge on your way up to the new 82nd floor observation deck.
Tickets are in limited supply and are sold on a first come, first serve basis and sell out quickly.
To get a same day ticket it's best to show up well before the sales desk opens at 8:30. If you get in line at 8:00 you should reach the front of it around 9:00 and should have several choices among the afternoon time slots.
If you aren't set on the idea of going up in the world's tallest twin buildings consider visiting the KL Tower instead.
Because it sits on a hill, the observation decks within the KL Tower is actually higher than the Twin Tower's 82nd floor observation deck.
Tickets to the observation deck of the KL tower are 45 MYR.
The KL Tower is open until 10:00 pm. While the latest you can get up in the Twin Towers is just before sunset, from the KL Tower you can get an excellent view of the city lit up at night.
The best deal is to buy a ticket to the KL Tower's revolving restaurant (50 MYR) at an off-meal time because it comes with a glass of wine or beer (normally priced at 32 MYR).