The other day I was invited to a party that started at 1 p.m. When I arrived there, the hosts have had prepared a cake for us.
Obviously, I wasn´t hungry at all/I felt no hungry/I was full, since I have had lunch a few hours before. However, in order to not be rude I accepted a piece of cake. I almost thrown up, but I ate it. Unfortunately/woefully, one of the hosts offered me another piece of cake.
I tried to explain that wasn´t hungry and that I have had lunch recently, but to no avail/I had no way out. She adds in my dish a piece of cake far bigger than the previous one.
I did'nt know what to do until I spotted/saw a trash bin/garbage can by me. I had then no doubt, when nobody was looking I spit up the cake crumbs in it.
I put “spit up”, for lack of a better word. Perhaps there´s another expression that expresses it. I thought
of “throw up” but then, on second thought I decided that “throw up” would be “to empty the content of the stomach” and it would be something somehow involuntary.