Answer
Regular Coke is heavier.
Work Step by Step
In order to create a box and whisker plot, use a box a whisker plot maker online. (To draw one by hand, draw a line, making the far left point the minimum and the far right point the maximum. Then, draw a box, where the left side of the box is $Q_1$ and where the right side of the box is $Q_3$. Finally draw a vertical line through the box: this is your median.) Doing this, we see that the box for the regular Coke is further right than the box for the Diet Coke, meaning that regular Coke is more dense.
