Go to Mauville City and ask Rydel for a bike.
The Bike Shop...........
Mauvile city at the bike shop.
In Mauville City
There's a bike shop in the city with the electric gym. Go inside, talk to the shop owner and choose your bike (mach or acro).
In mauville city next to the Pokemon center in the bike shop talk to the guy in green and the choose ur bike
The last house in mauville city to the right
When you get to Mauville city team aqua will be invading. They take the bike shop manager. After you defeat Team Aqua with your highly skilled Pokemon and rescue the bike shop manager he will take you back to his shop and offer you a bike.
at mauville city, Rydels bike shop,opposite Pokemon centre. talk to the green shirt guy
There is not a bike voucher in Pokemon sapphire
in malvill (sorry 4 spelling) go 2 the bike shop and talk 2 rydle (or somin like that) and he will give it 2 u 4 free!
you need to go to Mauville to get a bike an Acro bike or a Match bike
You can find it on mauville city, near the Pokemon center (there are bikes outside, it's really easy to find)