Aiyooo jangan risau lah, minum air kosong lepas air gula memang boleh je, air saja pun okay! Kalau rasa macam nak muntah tu mungkin sebab air gula tu terlalu manis or perut tak sedap, bukan salah air kosong, so your glucose tolerance test (GTT) result should be fine lah, tapi untuk pastikan, best you contact your clinic or doctor to double-check je, they might ask you to reschedule if they prefer to be cautious, but honestly most clinics won't invalidate it just for that. Relax mama, happen to quite a few of us during pregnancy, jangan stress sangat okay?