Palau - is a champagne/sparking wine (tiny) bar that has become super popular in Munich. They also have a short menu of a tapas and baguettes (bocadillos). But as a Spaniard myself and with my family coming from Barcelona, I would NOT recommend to have dinner there, the food is too simple... too primitive. It is good as a snack to accompany your glass of cava but that's it!
Itaxo tapas - there are a number of Spanish tapas bars in Munich. None has everything to be called the best Spanish bar in the city, but Itaxo is very close. It is authentic, it is affordable and it is run by Spaniards that have experience in Spanish kitchens. You need to book a table even during the week.
Teatro Tapas - is a fashionable tapas bar in the heart of Haidhausen, where you order your drinks at the table and for the food: you get a piece of paper and a pen, then you go to the bar counter (which is extremely long), where they display what's on the menu: paella, pulpo, tortilla de patata, champiñones al ajillo, etc. You write down the number of the racion/tapa that you'd like to order, you go back to your table and then order.