Washing up liquid
Ordinary washing up liquid is NOT a good substitute for a proper car wash or wash and wax product. Most of them have all sorts of additives to keep your hands soft and these end up as a thin film over your paintwork and stop you getting a good shine. If there is nothing else then get yourself a bottle of the “Basics” liquid from any big supermarket. The reason it is about 15p for a litre bottle is they put very little in it, so it has less to reduce the shine, it is also great for cleaning alloy wheels.