Bit of speculation on my part
I think the 750 kW Megachargers Pepsi is using is the Supercharger V4 (which isn't actually a V4, but a V3, and not the true Megacharger that will be used for long haul routes that will charge 10-80% in 30 minutes
My reasons are that given the expected Cybertruck pack size (~216 kWh by my latest dive into it, probably a bit more usable vs gross), 750 kW is in the ballpark of what we would expect it would charge at just extrapolating from previous Tesla models
Also, why would Tesla put the time into a 750 kW charger that won't used much once the also extrapolating from current vehicles 2.5~3 MW charger needed for the 30 minutes 10-80% charge time?
There is also the chance that Pepsi is time and time again misquoting the 750 kW charge rate
To go a bit deeper, on Modesto the cabinets looks just like V3 ones and there is 8 of them, each can pull 350 kW from the grid, so for 4 stalls it's 700 kW for each stall, but V3 can share a DC bus between multiple cabinets up to 575 kW, so each cabinet could pull 925 kW total if adjacent cabinets are not being used and from the Megapack they have there also, for a total when a maximum of 2/4 stalls in use 1850 kW, so that doesn't make sense with Pepsi 750 kW quote
Going a bit more, Supercharger V4 might be one Supercharger V3 cabinet per stall, that when paired with the output of a Megapack could supply 925 kW per stall, and considering you rarely will have vehicles arriving empty at the same time, one Megapack could have enough power 6 to V4 stalls
So a bunch of info and we arrived nowhere, how much do you guys think we need to pay a Pepsi driver to record a charging session undercover?