My dog is sick & can't keep anything down?

Yesterday & today she's been throwing up, all her food & water so I took the food away & iv been giving her a bit of water today & she threw it up. I'm still going to take her to the vet & everything but any idea what might be wrong? I don't think she ate anything outside but with her I never know & she's a lab & shar-pei mix, she is around 40-50 pounds