The singer and reality TV star is believed to have managed to sing one song before vomiting when she visited the USS Harry S Truman near Doha, Qatar on October 1.
An insider told Us Weekly: “She flew in on a helicopter and had three Red Bulls with no water.”
Another source said she was 'dehydrated and got sick before she performed - and even got an IV. The doctor told her not to sing, but she did anyway.'
Returning from her trip, Simpson tweeted: 'Feel so humbled by the sacrifice the troops and their families make to keep us safe. I'm forever changed after this last week. Thank you.'