Could I have a glass of water, please?
Mi porta un bicchiere d’acqua, per favore?
能给我拿杯水吗?

Could I have a straw, please?
Mi porta una cannuccia, per favore?
能给我拿根吸管吗?

Enjoy your meal/Bon sppetit!
Buon appetito!
就餐愉快/胃口好!