stick your bike
As he walked home, Liesel picked the ball up and placed it under her arm. She could hear him call out, “Hey,
Saumensch.” She waited. “Saumensch!”

She relented. “What?”

“I’ve got a bike without wheels here, too, if you want it.”

“Stick your bike.”

From her position on the street, the last thing she heard was the laughter of that Saukerl, Rudy Steiner.

What does "stick your bike"here mean?

Question

stick your bike
As he walked home, Liesel picked the ball up and placed it under her arm. She could hear him call out, “Hey,
Saumensch.” She waited. “Saumensch!”

She relented. “What?”

“I’ve got a bike without wheels here, too, if you want it.”

“Stick your bike.”

From her position on the street, the last thing she heard was the laughter of that Saukerl, Rudy Steiner.

What does "stick your bike"here mean?

Answer

This is a colloquial expression, meaning "damn your bike".

It is quite rude, the NSFW literal meaning is "stick you bike where the sun don't shine" which would mean the speaker is referring to sticking the bike up your bottom. This is both insulting, and colloquial.

I hope this helps~