I have found this pretty helpful in boosting your sight reading.
Target improving Sight reading in two ways, Speed and Accuracy. To increase speed of reading, we take music that is relatively easy for us, and sight read it at tempo, neglecting rhythm and dynamics. It should sound nothing like the piece, you just play notes. Very important not to correct yoruself or go back, just keep going and dont look at your hands, and just don't stop if you make mistakes.
Improving Accuracy, take out hard music, play at pathetic super slow tempo, play with 100% note accuracy and finger accuracy.
I think this is the broad way to improve your reading. Then you have to learn not to read the black dots as we first do, but spaces made with them instead., that way increases your efficiency of absorbing what you see.