There are options for showers lower down on the trail, if you decide to use them, however, many people keep clean by using baby wipes and a bowl of warm water each day.
All accommodation on our trek to Everest Base Camp is in small tea houses, run by the local Sherpa people.  You will have a bed to sleep in (albeit not the most comfortable bed in the world, but a bed to say the least), in a twin-shared room.  There are options for showers lower down on the trail, if you decide to use them, however, many people keep clean by using baby wipes and a bowl of warm water each day.  The toilet situations can be difficult at times, some of the tea do not have Western-style toilets, rather just a hole in the ground instead of a toilet bowl. Be prepared for the different cultural experiences you will have along the way!