I shot this by taking two wine glasses and taping them end-to-end and setting them in a large pan (to catch the liquid)
Then I put my softbox with the 430exII directly behind it to rimlight the glass. Once I got that, I made some koolaid and started pouring.
I had the camera tethered and had a remote shutter trigger attached. I shot it in continuous mode.
I tilted the camera to get the "corner to corner" effect.