I booked an overnight bus from Nha Trang to Hoi An with Asia Smile Travel company. It broke down at 1am in the morning, over the next 9 hours we were provided no information except it would take 2 hours to fix - 9 hours later we were still waiting. We had no access to water or food. We had to sit on the side of the road as the bus became too hot because the airconditioning was not able to be used.
My brother was ill and was not able to take medication due to the lack of food and water.
At 9.45am we were over the lack of communication and after several attempts at waving passing vehicles down another tour bus company stopped, they charged us $15US each but at least were on the road again. Some of the other passengers were picked up by private cars and I don't know how they got on. We were taken to within 14km of Hoi An then dropped on the side of the road. I phoned our wonderful hotel in Nha Trang to help with the language barrier and arrange a taxi to come from Hoi An to pick us up.
We were unsure about getting on the bus in the first place because while we were waiting to board there was a major fuel leak happening, this turned out to be caused by no diesel cap - VERY DANGEROUS!!!
I think it was a sign and we should have pulled out at that stage and asked for a refund.
Anyway I would not travel with this company again and in fact there is only 1 bus company I will ever use and if they are not available I will take the train or fly.