Test for flooding.

[tower]

The brushless automatic car washes (with the arch that moves forward and back over your truck) shoot water at pretty high pressure. It's normal for a few drops to leak in through the sunroof with that much pressure. But it sounds like your leak is probably at the grommet(s) on your A pillar(s) under a front, side marker light. This is especially likely if you have roof lights, a CB or anything running wires through the A pillar, but could be the problem regardless. There are extensive threads on this site you can search regarding these leaks. So any of the techniques mentioned, or anything else that would run a high volume of water over your truck in a short period of time should suffice.