Jars used as glasses is a tendency that keeps growing. To give them a different touch, you can customise them with different techniques such as: decoupage with napkins, spray paint, acrylics, stamps, viniles, etc.
To do decoupage you only need some glass like varnish, a brush, napkins and a nylon bag. Put some varnish over the clean surface of the jar. Then, stick the napkin, taking special care not to leave any wrinkles or bubbles. To do so, pass the nylon bag over the napkin; then let it dry for a couple of hours. In the end, give them a coat of glass like varnish to protect them.