The need to drink 2-3 litres of water per day is a pseudoscientific myth.
Everyone's body is different. Some people have a metabolism that needs only 1 litre of water per day. Some need 2 litres. If you run a marathon in a hot temperature, you may need 5 litres.
Also, losing weight follows a simple rule in any diet. You need to have a calorie deficit per day. If your body needs 2000 calories per day to stay at the current weight, then you need to eat less than 2000 calories per day to lose weight.