保持卫生干净的英语句子包括：

1. Keep the environment clean and hygienic.

2. Keep the surroundings clean and hygienic.

3. Please keep the bus clean.

4. Please keep the MRT clean.

5. Please keep the park clean.

6. Please keep the beach clean.

7. Please keep the mountain clean.

8. Keep it clean.

9. Maintain cleanliness.

10. Stay hygienic.

这些句子可以根据不同的场合和需要选择使用。例如，第一个句子适合用于一般的环境卫生讨论，而第三个句子则适用于具体的公共卫生场合，如公交车、地铁、公园等。