Topping up Barrels

[LtCellars]

Hello, I'm trying to find out what people use to top up there barrels without there source going bad.
I usually open a bottle, top up and have whats left with dinner. But I have two 1 gallon jugs I would like to use for topping but do not want to create the head space in the jugs.
Thank you
Steve

 

[AlFulchino]

lot of folks use marbles in small jugs

 

[Wade E]

Maybe you should use 1 of those wine on tap containers as there is a bag in there that collapses on itself removing your top up jug problem.

 

[LtCellars]

Wine on Tap, I like that idea. I will have to do a search for them.
Thanks
Steve