I use a carbonator cap on a pop bottle filled with whatever cleaning fluid I'm using.
I attach the carbonator cap to the beer out line, open the tap, and squeeze the bottle.
Cleaning fluid then travels through the beer-lines and out the tap.
Simple and cheap! Plus the carbonator cap is fun to play with when your not cleaning.
Note, carbonated lemonade is good, carbonated milk is not!
God's own drunk, and a fearless man.