Yes no problem
Look at the ingredients in soap etc many are same as fertilisers eg phosphates.
The rest are harmless otherwise you would be dead.
A birdbath is typically a shallow bowl filled with water that is either on the ground or on a pedestal. Birds will use the water to drink or take a bath. You can purchase a bird bath at your local garden store.
A hot water bath is a bath with hot water. You use it to take a bath.
You don't use it in your bath water.
As far as it being safe for the birds to drink, yes either tap water or water from your garden hose is fine. The only issue you might have is the need to clean water scale and mineral build-up from the bird bath on occasion; use diluted bleach to clean it.
because to have a bath look nice and clean
It depends on the shower heads, bath heads, and the person. If you take a long shower, and use little water for a bath, bath is better. If you use a lot of water for a bath and take short showers with water saving heads, a shower would be better.
generally no unless .. your unit has a garden type location for it
You can use garden water in a variety of ways. One obvious way is to water your lawn and garden. Another way is to gather the rain runoff in special water purifying urns for use in bathing or cleaning.
hot water
Usually a bath but depends on the depth of the bath and the lenght of the shower
Wash up in a bowl - instead of the sink. Only use the washing machine when you have a full load. Use a shower instead of a bath. Only water the garden when absolutely necessary.
is it safe to take a bath in rubbing alcohol.