YOU SAID:
please may i have a glass of juice
INTO JAPANESE
私はジュースを一杯飲んでください
BACK INTO ENGLISH
I have a glass of juice
INTO JAPANESE
私はジュースを一杯飲んでいます
BACK INTO ENGLISH
I am drinking a glass of juice
INTO JAPANESE
私はジュースを飲んでいます
BACK INTO ENGLISH
I am drinking juice
INTO JAPANESE
私はジュースを飲んでいます
BACK INTO ENGLISH
I am drinking juice
That didn't even make that much sense in English.