And, of course, no sitting down to eat them!!!

Nobody cares what you drink in tapas bars in Spain. And if you want tap water, you can also ask for that (aqua de grifo). I like to have water with my meal even I'm drinking something else (soft drink or alcoholic). Everywhere I went, I drank tap water and it was fine.
The only thing that you do need to do is enjoy yourself. And that's not difficult to do at any tapas bar!

Sorry - agua de grifo.