Explanation for international readers:

In Sweden we have the seasonal beverages Julmust and Påskmust for Christmas (Jul) and Easter (Påsk) respectively. It's a dark musty carbonated soda from fruit juice and herbs (Must) and they are in almost every home at holiday time.

With this in mind, Mayomust is not the most clever marketing here. Unless they expect a consumer base of carbonated mayonnaise beverages to go yum.