A 40% discount is available for you if you vandalise Lindell's inspection shop (when Fleetari calls you) however, if you play between December 24th - 26th there is a 75% discount, you can probably see where this is going.

This section will be for Windows 10 (probably will work on 11 too)

Step 1) Type in "change date and time" into the search bar (or just date as that works)

Step 2) Disable "Set the time automatically"

Step 3) Press "Set the date and time manually" button

Step 4) Change the date to this (year doesnt matter for the discount)
Step 5) Go to Fleetari's and order something

Step 6) Repeat after 2 days

Source of the information was the MSC fandom.

Enjoy your day.