If you dig deep enough you can usually find some info on discharge rates but it’s still difficult as many cars are getting lots of software updates (the Kona had an update & the 12V battery gets a boost from the traction battery every 4 hours). The worst cars for discharge over a few weeks are Teslas which use up a small percentage of the traction battery each day, so need to be topped up before you leave them for a few weeks.
So you’d be wanting to arrive near the airport, top up the traction battery to around 90% on a rapid & then park up & leave it with the high state of charge.
With other manufacturers it’ll be different again, but the problem is usually the 12V battery. The problem occurs because of the way these EVs work, the 12V battery is used to energise a relay to switch the traction battery on, if the 12V battery fails then you also lose the traction battery. The 12V battery also needs the traction battery to charge from so if it falls to low then the car won’t start at all, although you’ll get the dash electrics come on & probably a fault showing on the dash.
The solution to the 12V battery not having enough voltage to open the main relay is a “jump start” from the RAC, or, to carry a spare battery of some sort, I have 4 LiFePO4 15AH cells in series pack (looks like sticks of dynamite), so effectively an equivalent “12V” 15AH battery that I can croc clip in series with the car’s own 12V battery as needed & the discharge rate of those LiFePO4 cells is very very slow (top them up once a year & all is fine). It’s not the sheer cranking current of a 12V lead acid battery that is needed in an EV, it’s a constant high enough voltage, hence the 15AH is extreme but I had 80 of those cells laying around unused.
So, an answer to your original question will be a few percent drop in the traction battery charge per week maximum, & it will be the 12V lead acid battery that fails first on most EVs.