1 litre of water weigh approx 948 gram, so 2 litre will weigh around 1.896 kg.
2 Litre Water Bottle
The water weighs 2 kilos and if it’s a plastic bottle allow a few grams for it.
2l Water Bottle
Roughly 2 kilos,,
Liter = volume
kilogram = mass
Since these are measures of different quantities, you cannot convert between them. This is like saying “How can I convert desks to grapes?”
Now if you are talking about a particular substance, you can get around this by the definition of density:
density = mass/volume
so if you know the density of your material you can find the mass by:
mass = density*volume
2 litres of water is two kilogrammes or 4.409 pounds