GD test help!

Okay guys, so my doctor is putting me straight into the 3 hour test because I'm high risk and instead of wasting time with two appointments, she's just going to do the one long appointment. Here is my issue. She told me to try to eat low carbs and high protein the days before the test for the most accurate results. But I have Hyperemesis gravidarum and am supposed to be eating high carb and low fat. I have no clue what to eat! One of the only things I can keep down is sandwiches...which are high carb. Help!