Why does the weight of opened cold coke change over time?

[Himal kharel]

A bottle of coke was taken out of refrigerator. It was then kept in a sensitive weighing balance.Its cap was opened. The initial weight was found to be 2.403 kg. After a while its weight increased to 2.423 kg. Then again it started decreasing.
I repeated this experiment for many times. And the result was the same the weight first increased and then started decreasing.
But I think that the weight must plainly start to decrease because the coke molecules will evaporate.
Please explain this fairly contradictory result to me.

 

[johnbbahm]

It sounds like the cold Bottle attracted condensation, as the bottle warmed the condensate evaporated.

 

[xts]

Interesting... I may believe it is a water condensating on the bottle.

To check this hypothesis - try the same experiment, but do not open the bottle.

And as soon as it reaches maximum weight - wipe it with a towel and put back on the balance.

EDIT>>>
I hardly may believe that different bottles of Coke have their weight identical up to 1g accuracy.