Really short, not that complicated, and I'm quite lazy, so I'm not going to follow the form.
Basically, this is how you do it.
Use a character with a special attack buff (I used Yoshi's Egg Charge)
Then, have a red cola
Use the special attack buff, then use the red cola
The effects of the special attack seem to wear out when the cola does, even though it shouldn't, because the special attack lasts longer
I'm not sure if this works with blue colas, and def buffs, but I'm going to have to find the time to see if it works for that too. I did this 3 times in a row and all 3 times produced the same results, in which both buffs disappeared when the cola buff went away, even though Egg Charge lasts much longer.
Thanks for reporting this; we actually know about it already. We don't technically have a real buff/debuff system, which is why it occurs. Kimi and I have discussed creating a real buff/debuff system, so this glitch would be fixed once that happens, but we're still not completely sure whether we're going to create it or not.