Need to know how l can empty the old gas from the gas tank on a 1988 Porsche 944? l think water might have gotten into the tank. If so what can l do to fix this problem. Please assist.

Drive it.

get a long tube and suck on it to siphon, but do no drink the gas

To get gas out of the tank u will have to drop the tank . If u think there mite be a little water in the gas then u can buy a can of treatment for the gas but that is not the best or sure fix way. You can find a good spot where the gas hose is rubber(before or after the fuel pump) & get a fuel water separator filter at a place like Boaters world or a Marine West store & but it on the car some where before the gas get to the injectors. Run the tank bone dry & re-fill. You may have run the car on blocks to make sure all the gas can get to the gas pickup point in the tank. If u can find a good spot to leave the filter u get at Boaters world the l would leave l would leave it there & this way u have the standard factory fuel filter plus the new one u put on that does water & fuel both. Just change them every 15,000miles or so & u will be fine.

l believe there is a circular plate at the lowest portion of the tank with screws surrounding it. if you take the plate off all of the gas will drain out.

It is not going to stall with a quarter cup of water in a 16 gallon tank.
Fill the tank with premium and put a line separator before the fuel pump and it will do it is own thing. If you live in a climate where freezing is present, replace the separator in a week. After that you can remove it, because the water will be gone.