The German team's riders, who were not identified by name, were hit by the car on a minor road near Alicante and two helicopters were used in the rescue, emergency services for the Valencia region said on their Twitter feed (@GVA112).
The riders involved were of various nationalities and between 18 and 27 years old while the two with more serious injuries had sustained multiple fractures, they added.
Giant-Alpecin said all the team's riders were in a "stable condition".
"There was an accident in training today at our camp in Spain," the team said on Twitter (@GiantAlpecin).
"Some riders involved in the crash went to the hospital for a check," they added. "More details to follow." (Additonal reporting by Emma Pinedo, writing by Iain Rogers, editing by Ken Ferris)