I will pick the middle 1 as 

1) The one on the left is cracked and the assassin won't pick a cracked jar fearing that the king might not pick it.

2) The one on the right is tilted meaning someone hast already spilled most of it or drank it and hence the king will not want a half filled jar

3) Hence its the middle 1 since its upright and looks new and chances the king will pick that up to drink.

middle one

It,s the tipped over one.It,s empty!

one on the right

I would say the third one,it's tip over

It is time to announce the result of our competition!

3,000 Emeralds are going to WIDORAX!

Congratulations!