Open the sunroof.
Look at the the track underneath. There is a channel to catch the water that gets by the seal. See the deflector that pops up when you open the glass? That's the water channel underneath it. The sunroof glass seal isn't supposed to stop all the water...just most of it. What gets by the channel catches.
At the corners, you'll see a hole....that's where the water drains out...there's a tube that goes down each 'A' pillar to the ground. There are also two rear tubes, but they don't get used much unless you park with the nose uphill....the fronts do the majority of the draining.
Anyway, take a bottle of water, and pour it in the channel near the drain hole...enough to cover the hole. See if it drains out, and how fast. Water should come out on the ground behind the front tires.
If the water level barely drops or doesn't drop at all, the tube is clogged up and you need to clear it. You can use compressed air and fix it sometimes.....sometimes you have to take it loose, which would involve dropping the front corner of the headliner to access it. (Not a big deal, but I do this every day)
You didn't say where you actually saw the water coming from, but the sunroof is usually where I start. The windshield or roof seams could also cause this problem.
Very unlikely the door seals could, unless the car is very old.
Get me some specifics on the leak location