3 sentences

1. 运动员必须提供尿样进行兴奋剂检测。

   yùn​dòng​yuán bì​xū tí​gōng niào​yàng jìn​xíng xīng​fèn​jì jiǎn​cè.

   Athletes must provide a urine sample for doping tests.

   Source: Dong Chinese Dictionary

2. 由于兴奋剂检测呈阳性，这名运动员被禁赛了两年。

   yóu​yú xīng​fèn​jì jiǎn​cè chéng yáng​xìng, zhè míng yùn​dòng​yuán bèi jìn​sài le liǎng nián.

   The athlete was banned for two years after testing positive for performance-enhancing drugs.

   Source: Dong Chinese Dictionary

3. 咖啡因是一种中枢神经系统兴奋剂。

   kā​fēi​yīn shì yī zhǒng zhōng​shū shén​jīng xì​tǒng xīng​fèn​jì.

   Caffeine is a central nervous system stimulant.

   Source: Dong Chinese Dictionary