If something is sportier, it means it is more like sports or is better for sports.
Sportier things are usually more fun and exciting.
Examples:
The red car is sportier than the blue car.
She bought a sportier bike for racing.
I want a sportier jacket for running.
My brother thinks his toy car is sportier than mine.
Her new shoes are even sportier than her old ones.
The sportier bike is faster than the other one.