I've used pastry bags for choux paste, potatoes, vegetable purees, frostings, whipped cream, etc. They wash up very easily in a sink with hot water & a little dish soap.
Most pastry bags have a plastic type lining. If you don't want the clean up, there are 2 other methods I've used.
1. Cut the corner off a large zip-lock food storage bag.
2. Make a cone (called a coronet) from a large square of parchment paper, and clip the point off.
You can insert a pastry tip into any of the 3 (pastry bag, plastic bag or parchment cone) before filling to make your piping decorative.