Olympic Cycling action clarification

They are riding for hours burning lots of calories. They need to take in food. They carry it in pouches in the back of their jersey.

They were either throwing away empty packages or throwing away full packages to lighten their load at the end of the race.

Actually, if you look closely you will see they are tossing their water bottles. Somewhere in the last few kilometers riders decide that they will not have time to hydrate any more and the race is on. Dumping the bottles removes bulky items from the jersey and reduces weight.

I saw that too and I think they were just getting rid of their extra food before the last few kilometers. At that point it's really too late to eat and they probably tossed them away just to lighten their load going up the last climb.