The best way to keep your plants watered while you are away is to sit them in a cereal bowl or other deep saucer and fill the saucer with water.
I find an inch of water will keep the plant soil damp for a week.
Mixing some sphagnum moss in the soil, or using just sphagnum moss if they are orchids will keep the plants from needed to be watered as frequently.
Remember this is what to do if you are going away. If you keep your house plants sitting in water all the time they will rot.
Keep your plants alive while you are on vacation