What's the best way to learn to read guitar sheet music.?

One note at a time. The rhymes out there that match a word with each line or space slow most people down because they have to sit there and work out the rhyme, think of the first letter of the word that matches a line or space, and then think about where that pitch is on their instrument. The result is reading music like you are working out a math problem rather than reading it like you would a story. Pick a pitch that is an open string on your guitar (e.g. your G string, second line from the bottom of the staff). Look at the note while playing it and saying "G." Do it over and over. This connects note name, finger placement, and staff position as one concept instead of three separate concepts. Then, add A (second fret, second space of staff) and do the same thing. Alternate between G and A. It's not going to click in a day. It will probably take a couple of weeks, but if you do it that way instead of trying to come up with a shortcut, you are going to be much better at sight reading (an absolutely necessity when playing in a school band).