Hey,
Since you are in your 27th week, you cannot take yourself and the baby for granted. You got to eat on time, no matter what. So, make sure this kind of day does not happen again.
For now, I think it can be acidity or gastric as you practically did not eat anything and the little that you had may have added to make you acidic. After having food and having a good night sleep, you still do not feel better, I suggest you please visit your gynaecologist and seek his advice.
Tresa Lim