How to get ‘All Upright’ ribbon for Food Fight level 15 (Melony Offense)

You're going to need a Lancer, plus your normal soldiers. The Lancer unit can 'detect' the invisible units, which will allow your normal soldiers to kill it. However, by itself the detector unit will not be strong enough to defeat the invisible enemies.

First, let me mention that this is a poorly designed game. I'm mentioning that not as a matter of opinion but to make the point that this game is a bit difficult to work with and levels like this one can seem "impossible". I'll cut short the list of gripes that I had playing this game, with the exception of mentioning that the screen tapping mechanism seemed to be rather buggy which likewise made controlling the qube quite difficult at times.

Regardless, I have managed to come up with a strategy that does solve Level-8. This level is laid out with a series of five platforms. Below, I've outlined a path that you can follow to get to the final door. This is difficult, but it can be done.

The idea is to hop to the first platform following the yellow line, next the blue and finally the red path. Sorry, the arcs that I have drawn do not follow the exact arcing path that your qube should follow in the air but they are a good generalized outline of how the qube should float from platform to platform.

You don't want to use a lot of power when you launching your qube. You want them to just barely land on the next level, near the middle of the platform, almost sliding on the inner edge toward the middle.

Be cautious and follow the path below and you will make it to level 9... where a new obstacle will be added to make this game a bit more interesting. ;)