There's a drain screw in the float bowl (no.32
here).Undo that and the bowl will drain. If you can find a way of catching it in a jar you could let it settle and examine it for any signs of water.
Any water in the tank tends to sit in the bottom of the tank at the rear and when the bike is on the sidestand the water rolls across to the fuel outlet. Drain the hoses between tank and fuel pump, and fuel pump and carbs, and also the float bowls while the bike is on the sidestand. Then lean the bike over to the right and try starting it. Any water in the tank will roll over to the other side of the tank away from the fuel outlet. If it starts and runs ok with the bike in that position but then after a short while back on the sidestand it splutters and dies, then I'd suggest getting the tank off and draining it completely.