He hated sword practices with Zuko. The guy took them way too seriously. And, besides, wasn't he Aang's teacher? Why was he there, then?
Besides, annoyed Zuko with a sword was more dangerous than annoyed yet unarmed Zuko. Oh well, there was nothing he could do.
'Oh, come on. Is that all you can do? I could beat you even without a sword.'
'Then show me that, you idiot.'
Sokka shrugged.
'No way. You have Firebending.'
'I won't use it.'
Fifteen minutes later, all sweaty and laying on top of Zuko, he decided the practices weren't so bad.